51 nod 乘法逆元

http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1256

#include <iostream>

using namespace std;
typedef long long LL;
void exgcd(LL a, LL b, LL &x, LL &y)//扩展欧几里得算法
{
    if(b == 0)
    {
        x=1;
        y=0;
        return ;
    }
    exgcd(b, a%b, x, y);
    LL tmp=x;
    x=y;
    y=tmp - (a/b)*y;
}
int main()
{
    LL m,n,x,y;
    while(cin>>m>>n)
    {
        exgcd(m, n, x, y);
        while(x<0)//当x<0时还要转换为正数
            x+=n;
        cout<<x<<endl;
    }
    return 0;
}