#include <bits/stdc++.h> using namespace std; long long maximum(long long a, long long b) { if (a > b) return a; return b; } int main() { int n; cin >> n; long long answer = 0; for (int i = 0; i < n; i++) { long long a, b; cin >> a >> b; answer += maximum(a, b); } cout << answer << '\n'; }