{"trustable":true,"prependHtml":"\u003cstyle type\u003d\u0027text/css\u0027\u003e\n .input, .output {\n border: 1px solid #888888;\n }\n .output {\n margin-bottom: 1em;\n position: relative;\n top: -1px;\n }\n .output pre, .input pre {\n background-color: #EFEFEF;\n line-height: 1.25em;\n margin: 0;\n padding: 0.25em;\n }\n \u003c/style\u003e\n \u003clink rel\u003d\"stylesheet\" href\u003d\"//codeforces.org/s/96598/css/problem-statement.css\" type\u003d\"text/css\" /\u003e\u003cscript\u003e window.katexOptions \u003d { disable: true }; \u003c/script\u003e\n\u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n MathJax.Hub.Config({\n tex2jax: {\n inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027], [\u0027$\u0027,\u0027$\u0027]],\n displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027], [\u0027$$\u0027,\u0027$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript type\u003d\"text/javascript\" async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS_HTML-full\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"HTML","content":"\u003cp\u003eA company has \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e employees numbered from \u003cspan class\u003d\"tex-span\"\u003e1\u003c/span\u003e to \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e. Each employee either has no immediate manager or exactly one immediate manager, who is another employee with a different number. An employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eA\u003c/i\u003e\u003c/span\u003e is said to be the \u003cspan class\u003d\"tex-font-style-underline\"\u003esuperior\u003c/span\u003e of another employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eB\u003c/i\u003e\u003c/span\u003e if at least one of the following is true:\u003c/p\u003e\u003cul\u003e \u003cli\u003e Employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eA\u003c/i\u003e\u003c/span\u003e is the immediate manager of employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eB\u003c/i\u003e\u003c/span\u003e \u003c/li\u003e\u003cli\u003e Employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eB\u003c/i\u003e\u003c/span\u003e has an immediate manager employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eC\u003c/i\u003e\u003c/span\u003e such that employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eA\u003c/i\u003e\u003c/span\u003e is the superior of employee \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eC\u003c/i\u003e\u003c/span\u003e. \u003c/li\u003e\u003c/ul\u003e\u003cp\u003eThe company will not have a managerial cycle. That is, there will not exist an employee who is the superior of his/her own immediate manager.\u003c/p\u003e\u003cp\u003eToday the company is going to arrange a party. This involves dividing all \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e employees into several groups: every employee must belong to exactly one group. Furthermore, within any single group, there must not be two employees \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eA\u003c/i\u003e\u003c/span\u003e and \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eB\u003c/i\u003e\u003c/span\u003e such that \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eA\u003c/i\u003e\u003c/span\u003e is the superior of \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003eB\u003c/i\u003e\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eWhat is the minimum number of groups that must be formed?\u003c/p\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003eThe first line contains integer \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e (\u003cspan class\u003d\"tex-span\"\u003e1 ≤ \u003ci\u003en\u003c/i\u003e ≤ 2000\u003c/span\u003e) — the number of employees.\u003c/p\u003e\u003cp\u003eThe next \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e lines contain the integers \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ep\u003c/i\u003e\u003csub class\u003d\"lower-index\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/sub\u003e\u003c/span\u003e (\u003cspan class\u003d\"tex-span\"\u003e1 ≤ \u003ci\u003ep\u003c/i\u003e\u003csub class\u003d\"lower-index\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/sub\u003e ≤ \u003ci\u003en\u003c/i\u003e\u003c/span\u003e or \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ep\u003c/i\u003e\u003csub class\u003d\"lower-index\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/sub\u003e \u003d \u003c/span\u003e-1). Every \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ep\u003c/i\u003e\u003csub class\u003d\"lower-index\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/sub\u003e\u003c/span\u003e denotes the immediate manager for the \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/span\u003e-th employee. If \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ep\u003c/i\u003e\u003csub class\u003d\"lower-index\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/sub\u003e\u003c/span\u003e is -1, that means that the \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/span\u003e-th employee does not have an immediate manager. \u003c/p\u003e\u003cp\u003eIt is guaranteed, that no employee will be the immediate manager of him/herself (\u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ep\u003c/i\u003e\u003csub class\u003d\"lower-index\"\u003e\u003ci\u003ei\u003c/i\u003e\u003c/sub\u003e ≠ \u003ci\u003ei\u003c/i\u003e\u003c/span\u003e). Also, there will be no managerial cycles.\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003ePrint a single integer denoting the minimum number of groups that will be formed in the party.\u003c/p\u003e"}},{"title":"Examples","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003e5\n-1\n1\n2\n1\n-1\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e3\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Note","value":{"format":"HTML","content":"\u003cp\u003eFor the first example, three groups are sufficient, for example: \u003c/p\u003e\u003cul\u003e \u003cli\u003e Employee 1 \u003c/li\u003e\u003cli\u003e Employees 2 and 4 \u003c/li\u003e\u003cli\u003e Employees 3 and 5 \u003c/li\u003e\u003c/ul\u003e"}}]}