参考http://blog.csdn.net/polossk/article/details/9799735
package acm; public class FrogDate { public static void main(String[] args) { int x = 11,y = 21,m = 31,n = 41,l = 44; int ar=n-m,br=0,cr=x-y; int M = exGcd(n-m,l,ar,br); System.out.println("M:" + M); if((x-y)%M!=0 || m==n) System.out.println("Impossible"); else{ int s=l/M; ar=ar*((x-y)/M); ar=(ar%s+s)%s; System.out.println("ar : " + ar); } } static int Gcd(int a, int b) { while(b != 0) { int r = b; b = a % b; a = r; } return a; } static int exGcd(int a, int b, int x, int y) { if(b == 0) { x = 1; y = 0; return a; } int r = exGcd(b, a % b, x, y); int t = x; x = y; y = t - a / b * y; return r; } }