这道题就是考map用法的

#include <iostream>
#include <map>
using namespace std;
int main()
{
    int n;
    cin >> n;
    map<int, int> m;
    int ind, val;
    while (cin >> ind >> val) {
        m[ind] += val;
    }
    for (map<int, int>::iterator it = m.begin(); it != m.end(); it++) {
        cout << it->first << " " << it->second << endl;
    }
}