#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int x, y;
  int a[100000], b[100000];
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    a[i] = x;
    b[i] = y;
  }
  int maxi = a[0] + b[0];
  for (int q = 1; q < n; q++) {
    if (a[q] + b[q] > maxi) {
      maxi = a[q] + b[q];
    }
  }
  cout << maxi;
  return 0;
}
