#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cmath>

int main() {
    std::ifstream f("b");

    std::vector<int> x;
    std::vector<int> y;
    int l, r;
    
    while (f >> l >> r) {
        x.push_back(l);
        y.push_back(r);
    }

    std::sort(x.begin(), x.end());
    std::sort(y.begin(), y.end());
 
    long t = 0;
    int c = 0;
    auto p = y.begin();
    for (size_t i = 0; i < 4000000; i++) {
	    auto b = std::lower_bound(p, y.end(), x[i]);
	    auto u = std::upper_bound(p, y.end(), x[i]);
	    int c = u - b;
	    t += x[i] * c;
	    p = b;
    }

    std::cout << t;

    return 0;
}