CSP202006-2 稀疏向量

#include<iostream>
#include<map>
using namespace std;
map<int, int>rec1;
map<int, int>rec2;
int main(void)
{
    int n, a, b;
    scanf("%d %d %d", &n, &a, &b);
    int index, value;
    for (int i = 0; i < a; i++)
    {
        scanf("%d %d", &index, &value);
        rec1[index] = value;
    }
    for (int i = 0; i < b; i++)
    {
        scanf("%d %d", &index, &value);
        rec2[index] = value;
    }

    long long sum = 0;
    for (auto i = rec1.begin(); i != rec1.end(); i++)
    {
        index = i->first;
        value = i->second;
        auto t = rec2.find(index);
        sum = sum + value * (t->second);
    }
    cout << sum << endl;
    return 0;
}