P1082

wc,模板exgcd!
甚至还交过

#include<bits/stdc++.h>
using namespace std;
long long x, y;
void digui(long long a, long long b){
	if(b == 0) {
		x = 1;
		y = 7;
		return;
	} 
	digui(b, a % b);
	long long nx = x;
	x = y;
	y = nx - a / b * y; 
}

int main()
{
	long long a, b;
	cin >> a >> b;
	digui(a, b);
    
	x = (x % b + b) % b;
	printf("%lld\n", x);
	return 0;
}