#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  while (scanf("%lld", &n) == 1) {
    long long int a, b, sum, ans = 0;
    for (long long int i = 1; i <= n; i++) {
      scanf("%lld", &a);
      scanf("%lld", &b);
      sum = a + b;
      ans = max(ans, sum);
    }
    printf("%lld", ans);
    printf("\n");
  }
}
