扩展欧几里得算法

#include <cstdio>

int x, y, a, b;

void exgcd(int a, int b){
	if(b == 0) {
		x = 1, y = 0;
		return ;
	}
	exgcd(b, a % b);
	int xx = x, yy = y;
	x = yy;
	y = xx - (a / b) * yy;
	return ;
}

int main() {
	freopen("test.in", "r", stdin);
	scanf("%d%d", &a , &b);
	exgcd(a, b);
	printf("%d", (x %b  + b) % b);
	return 0;
}