#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  int x[n];
  int y[n];
  int maks = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &x[i], &y[i]);
    if (maks < x[i] + y[i]) {
      maks = x[i] + y[i];
    }
  }
  printf("%d\n", maks);
  return 0;
}
