acwing 203题解

#include <bits/stdc++.h>
using namespace std;
int x,y;
void ex_gcd(int a,int b)
{
    if(b==0)
    {
        x=1,y=0;
        return;
    }
    ex_gcd(b,a%b);
    int cx=x,cy=y;
    x=cy,y=(cx-a/b*cy);
}


int main()
{
    int a,b;
    cin>>a>>b;
    ex_gcd(a,b);
    cout<<(x%b+b)%b<<endl;
    return 0;
}