#include<bits/stdc++.h>
using namespace std;

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;
}

int main() {
int a,b,i,j,k,m,n;
cin>>m>>n;
int gcd=exGcd(m,n,a,b);
cout<<(a%n+n)%n;
return 0;
}

洛谷P1082同余方程