#include <bits/stdc++.h>
using namespace std;
int x, y;
long long ans;
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    scanf("%d%d", &x, &y);
    if (x + y > ans) ans = x + y;
  }
  printf("%lld", ans);
}
