#include <bits/stdc++.h>
using namespace std;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	vector<int> l1;
	multiset<int> l2;
	string line;
	while (getline(cin, line) && !line.empty()) {
		istringstream l(line);
		int a, b;
		l >> a >> b;
		l1.push_back(a);
		l2.insert(b);
	}

	long long result = 0;
	for (auto i : l1) {
		result += i * l2.count(i);
	}

	cout << result << '\n';
}