#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using vll = vector<ll>;
using vpll = vector<pll>;
using gr = vector<vll>;
using wgr = vector<vpll>;
struct d_ {
  template <typename T>
  d_& operator,(const T& x) {
    cerr << ' ' << x;
    return *this;
  }
  template <typename T>
  d_& operator,(const vector<T>& x) {
    for (auto x : x) cerr << ' ' << x;
    return *this;
  }
} d_t;
int main(void) {
  ios_base::sync_with_stdio(false);
  ll n;
  cin >> n;
  ll ret = 0;
  for (ll i(0); i < n; i++) {
    ll a, b;
    cin >> a >> b;
    ret = max(ret, a + b);
  }
  cout << ret << endl;
  return 0;
}
