{"trustable":false,"prependHtml":"\u003cstyle type\u003d\"text/css\"\u003e\n section pre {\n display: block;\n padding: 9.5px;\n margin: 0 0 10px;\n font-size: 13px;\n line-height: 1.42857143;\n word-break: break-all;\n word-wrap: break-word;\n color: #333;\n background: rgba(255, 255, 255, 0.5);\n border: 1px solid #ccc;\n border-radius: 6px;\n }\n\u003c/style\u003e\n\u003cscript\u003e\n window.katexOptions \u003d {\n delimiters: [\n {left: \u0027\\\\(\u0027, right: \u0027\\\\)\u0027, display: false},\n {left: \u0027\\\\[\u0027, right: \u0027\\\\]\u0027, display: true}\n ]\n };\n\u003c/script\u003e\n","sections":[{"title":"题意","value":{"format":"HTML","content":"\u003cfont color\u003dred\u003e一血产生者:罗新新\u003c/font\u003e\u003cbr\u003e\n蒋武和廖伟在一个二维平面上打台球,x轴充当墙,当球击中后,碰到墙壁会反弹,因此入射角等于反射角。蒋武的球现在在(Sx,Sy)。当他的球击向某一点时,球会沿着直线向那个点滚去。使球恰好击中x轴一次,然后通过(Gx,Gy),那么蒋武应该瞄准x轴上那个点进行击打?蒋武请求聪明的你帮助他。"}},{"title":"Input","value":{"format":"HTML","content":"输入一行包括四个整数Sx , Sy , Gx , Gy ( -10^6 \u003c\u003d Sx , Gx \u003c\u003d 10^6,0 \u003c Sy , Gy \u003c\u003d 10^6 ,Sx ≠ Gx )."}},{"title":"Output","value":{"format":"HTML","content":"打印一个数x——即坐标(x,0),当与我们的答案的绝对或相对误差不超过10^(-6)时,您的输出将被认为是正确的。"}},{"title":"Sample Input 1","value":{"format":"HTML","content":"\u003ch3\u003e\u003c/h3\u003e\n\u003cpre\u003e1 1 7 2\n\u003c/pre\u003e"}},{"title":"Sample Output 1","value":{"format":"HTML","content":"\u003ch3\u003e\u003c/h3\u003e\n\u003cpre\u003e3.0000000000\n\u003c/pre\u003e \n\u003cp\u003e如下图所示,我们可以通过瞄准(3,0)进行打击使球通过(7,2)。\u003c/p\u003e \n\u003cp\u003e\u003cimg alt\u003d\"Figure\" src\u003d\"CDN_BASE_URL/618a664a3ac94ef7de019ff54625f49e?v\u003d1627951070\"\u003e\u003c/p\u003e"}},{"title":"Sample Input 2","value":{"format":"HTML","content":"\u003ch3\u003e\u003c/h3\u003e\n\u003cpre\u003e1 1 3 2\n\u003c/pre\u003e"}},{"title":"Sample Output 2","value":{"format":"HTML","content":"\u003ch3\u003e\u003c/h3\u003e\n\u003cpre\u003e1.6666666667\n\u003c/pre\u003e \n\u003cp\u003e\u003cimg alt\u003d\"Figure\" src\u003d\"CDN_BASE_URL/1626a0c1a78de5af979927661b8fb826?v\u003d1627951070\"\u003e\u003c/p\u003e"}},{"title":"Sample Input 3","value":{"format":"HTML","content":"\u003ch3\u003e\u003c/h3\u003e\n\u003cpre\u003e-9 99 -999 9999\n\u003c/pre\u003e"}},{"title":"Sample Output 3","value":{"format":"HTML","content":"\u003ch3\u003e\u003c/h3\u003e\n\u003cpre\u003e-18.7058823529\n\u003c/pre\u003e \n\u003cp\u003e当输出与答案的绝对或相对误差不超过10^(-6)时,输出将被认为是正确的。\u003c/p\u003e"}}]}