POJ 1061 青蛙的约会(扩展欧几里德)

#include<cstdio>
#include<iostream>
#include<sstream>
#include<cstdlib>
#include<cstring>
#include<string>
#include<climits>
#include<cmath>
#include<algorithm>
#include<queue>
#include<vector>
#include<stack>
#include<set>
#include<map>
using namespace std;
long long t, p, c;
void ou(int a, int b)
{
    if(b == 0)
    {
        t = 1;
        p = 0;
        c = a;
    }
    else
    {
        ou(b, a%b);
        int temp = t;
        t = p;
        p = temp - a/b*p;
    }
}
int main()
{
    int i, j, flag = 0, d, a, b;
    long long x, y, m, n, l;
    scanf("%lld%lld%lld%lld%lld",&x,&y,&m,&n,&l);
    if(n == m)
        flag= 1;
    else
    {
        a = n-m;
        d = x-y;
        b = l;
        ou(a, b);
        if(d % c !=0)
            flag= 1;
    }
    if(flag)
        printf("Impossible\n");
    else
    {
        b = b / c;
        d = d / c;
        long long v = d * t;
        printf("%d\n",(v%b+b)%b);
    }
    return 0;
}