#include <bits/stdc++.h>
using namespace std;
int dx[8] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[8] = {0, 1, 0, -1, -1, 1, -1, 1};
int ini() {
  int x;
  scanf("%d", &x);
  return x;
}
long long inl() {
  long long x;
  scanf("%lld", &x);
  return x;
}
const int N = (int)1e5 + 5;
const int inf = (int)1e9 + 7;
int x[N], y[N];
int main() {
  int n, i, j, x1, y1, yy = INT_MIN, in;
  n = ini();
  for (i = 1; i <= n; i++) {
    x[i] = ini();
    y[i] = ini();
    int s = x[i] + y[i];
    if (s > yy) {
      yy = s;
    }
  }
  cout << yy << endl;
  return 0;
}
