一眼map

#include <iostream>
#include <map>

int main(int argc, char* argv[]){
    int n;
    std::cin >> n;
    int index;
    int value;
    std::map<int, int> map;
    while(std::cin >> index >> value){
        map[index] += value;
    }
    for(auto i : map){
        std::cout << i.first << " " << i.second << std::endl;
    }
    return 0;
}