#include <bits/stdc++.h>
using namespace std;
const long long inf = 707406378;
const int maxn = 1.5e7 + 10;
void read(long long &x) {
  char ch;
  bool flag = 0;
  for (ch = getchar(); !isdigit(ch) && ((flag |= (ch == '-')) || 1);
       ch = getchar())
    ;
  for (x = 0; isdigit(ch); x = (x << 1) + (x << 3) + ch - 48, ch = getchar())
    ;
  x *= 1 - 2 * flag;
}
int main() {
  long long n, x, y;
  cin >> n;
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    ans = max(ans, x + y);
  }
  cout << ans << endl;
  return 0;
}
