#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int N = 1e6 + 100;
int T;
int n;
pair<long long, long long> po[N];
int main() {
  scanf("%d", &n);
  long long x, y, maxx = 0;
  int whi;
  for (int i = 1; i <= n; i++) {
    scanf("%lld%lld", &x, &y);
    maxx = max(maxx, x + y);
  }
  printf("%lld\n", maxx);
  return 0;
}
