#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
int main() {
  int n;
  cin >> n;
  int maxn = 0;
  int x, y;
  while (n--) {
    scanf("%d %d", &x, &y);
    maxn = max(maxn, x + y);
  }
  cout << maxn << endl;
}
