#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int ans = 0;
  for (int i = 0; i < (n); ++i) {
    int x, y;
    scanf("%d%d", &x, &y);
    ans = max(x + y, ans);
  }
  printf("%d\n", ans);
}
