题解 | 大整数哈希

#include <iostream>
#include <unordered_map>
#include <vector>
using namespace std;

int main() {
    unsigned long long n;
    cin >> n;
    unordered_map<unsigned long long, unsigned long long> vc;
    // unsigned long long mod = 1ll << 64;
    // cout << mod << endl;
    unsigned long long ans=0;
    for(unsigned long long i=1; i<=n; ++i){
        unsigned long long x,y;
        cin >> x >> y;
        ans += (i*vc[x]);
        vc[x] = y;
    }
    cout << ans << endl;

}
// 64 位输出请用 printf("%lld")