#include <bits/stdc++.h>
using namespace std;
bool sortfunc(const pair<long, long> &a, const pair<long, long> &b) {
  return (a.second < b.second || (a.second == b.second && a.first < b.first));
}
bool binarySearch(int arr[], int n, int x) {
  int k = 0;
  for (int b = n / 2; b >= 1; b / 2)
    while (k + b < n && arr[k + b] <= x) k += b;
  if (arr[k] == x) return k;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  long n;
  long maxi = 0, x, y;
  cin >> n;
  for (int i = 0; i <= (int)(n - 1); ++i) {
    cin >> x >> y;
    maxi = max(maxi, x + y);
  }
  cout << maxi << endl;
  return 0;
}
