https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1432
#include <stdio.h> int main () { int a, b, c; while (scanf("%d%d%d", &a, &b, &c) == 3) { printf("%.5lf\n", (1.0 * a * b + b * (b - 1)) / (a + b - c - 1) / (a + b )); } return 0; }
原文：http://www.cnblogs.com/yifi/p/4547458.html
