#include <bits/stdc++.h>
using namespace std;
const long long mx = 100001;
const long long mod = 1000000007;
const long long inf = 0x3f3f3f3f;
void solve();
int main() {
  int t = 1;
  for (int i = 1; i <= t; i++) {
    solve();
    if (i != t) printf("\n");
  }
  return 0;
}
void solve() {
  long long x, y, m = 0, n;
  scanf("%lld", &n);
  while (n--) {
    scanf("%lld", &x);
    scanf("%lld", &y);
    m = max(m, x + y);
  }
  printf("%lld", m);
  ;
}
