一眼中国剩余定理，秒！

C++ 代码

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 15;
int m[N], a[N];
int exgcd(int a, int b, int &x, int &y){
    if (!b){
        x = 1; y = 0;
        return a;
    }
    int d = exgcd(b, a % b, y, x);
    y -= (a / b) * x;
    return d;
}
signed main(){
    int n;
    scanf("%d", &n);
    for (int i = 1; i <= n; i ++ ) scanf("%intd%intd", &m[i], &a[i]);
    int M = 1;
    for (int i = 1; i <= n; i ++ ) M *= m[i];
    int res = 0;
    for (int i = 1; i <= n; i ++ ){
        int x, y;
        int MM = M / m[i];
        exgcd(MM, m[i], x, y);
        res = (res + a[i] * MM % M * x) % M;
    }
    res = (res + M) % M;
    cout << res << endl;
    return 0;
}