#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) {
  int r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
long long int power(long long int a, long long int b) {
  long long int r = 1;
  while (b) {
    if (b & 1) {
      r = r * a;
      b--;
    }
    a = a * a;
    b >>= 1;
  }
  return r;
}
int palindrome(char *s, int len) {
  int i, j, k, count = 0, c = 0;
  for (i = 0, j = len - 1; i < len, j >= 0; i++, j--) {
    if (s[i] == s[j]) count++;
  }
  if (count == len)
    return 1;
  else
    return 0;
}
long long int binary(char *s, long long int len) {
  long long int i, j, k, r = 0, p = 0, num;
  for (i = len - 1; i >= 0; i--) {
    num = s[i] - '0';
    r += (num * power(2, p));
    p++;
  }
  return r;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int i, j, k, n, maxi = 0, x, y;
  string s1, s2;
  cin >> n;
  while (n--) {
    cin >> x >> y;
    maxi = max(maxi, (x + y));
  }
  cout << maxi << endl;
}
