90pts求助，WA on #4

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cmath>
using namespace std;
long long nn,a[15],b[15],m[15],m_[15],p;
__int128 ans,n = 1;
long long x,y,gcd;
void exgcd(long long a,long long b){
	if(b == 0){
		x = 1,y = 0;
		gcd = a;
		return ;
	}
	exgcd(b,a % b);
	long long t = x;
	x = y,y = t - a / b * y;
}
signed main(){
	scanf("%lld",&nn);
	for(long long i = 1;i <= nn;i++){
		scanf("%lld%lld",&a[i],&b[i]);
		n *= a[i];
	}
	for(long long i = 1;i <= nn;i++){
		m[i] = n / a[i];
		exgcd(m[i],a[i]);
		ans = (ans + (__int128)b[i] * m[i] * x + 3 * n) % n;
	}
	printf("%lld",ans);
	return 0;
}