#include <iostream>
#include <fstream>
#include <vector>

int main() {
    std::vector<int> vector;
    std::ifstream input("../input.txt");

    std::string line;

    while(std::getline(input, line)) {
        int num = std::stoi(line);
        vector.push_back(num);
    }

    for (int i : vector) {
        for (int j : vector) {
            if (i + j == 2020) {
                std::cout << (i * j) << std::endl;
            }
        }
    }

    return 0;
}