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