{"trustable":true,"sections":[{"title":"","value":{"format":"HTML","content":"Farmer John is assigning some of his N (1 \u0026lt;\u003d N \u0026lt;\u003d 25,000) cows to do some cleaning chores around the barn. He always wants to have one cow working on cleaning things up and has divided the day into T shifts (1 \u0026lt;\u003d T \u0026lt;\u003d 1,000,000), the first being shift 1 and the last being shift T.\u003cbr\u003e\u003cbr\u003eEach cow is only available at some interval of times during the day for work on cleaning. Any cow that is selected for cleaning duty will work for the entirety of her interval.\u003cbr\u003e\u003cbr\u003eYour job is to help Farmer John assign some cows to shifts so that (i) every shift has at least one cow assigned to it, and (ii) as few cows as possible are involved in cleaning. If it is not possible to assign a cow to each shift, print -1."}},{"title":"Input","value":{"format":"HTML","content":"* Line 1: Two space-separated integers: N and T\u003cbr\u003e\u003cbr\u003e* Lines 2..N+1: Each line contains the start and end times of the interval during which a cow can work. A cow starts work at the start time and finishes after the end time."}},{"title":"Output","value":{"format":"HTML","content":"* Line 1: The minimum number of cows Farmer John needs to hire or -1 if it is not possible to assign a cow to each shift."}},{"title":"Sample","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\u003e3 10\r\n1 7\r\n3 6\r\n6 10\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e2\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Hint","value":{"format":"HTML","content":"This problem has huge input data,use scanf() instead of cin to read data to avoid time limit exceed.\u003cbr\u003e\u003cbr\u003eINPUT DETAILS:\u003cbr\u003e\u003cbr\u003eThere are 3 cows and 10 shifts. Cow #1 can work shifts 1..7, cow #2 can work shifts 3..6, and cow #3 can work shifts 6..10.\u003cbr\u003e\u003cbr\u003eOUTPUT DETAILS:\u003cbr\u003e\u003cbr\u003eBy selecting cows #1 and #3, all shifts are covered. There is no way to cover all the shifts using fewer than 2 cows."}}]}