#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 10;
const long long mod = 1e9 + 7;
const int inf = 0x3f3f3f3f;
const long long lnf = 1e18 + 7;
const double pi = acos(-1.0);
const double eps = 1e-6;
inline void work();
int main() { return work(), 0; }
long long ans = 0;
struct node {
  long long x, y;
  inline void read() {
    scanf("%lld%lld", &x, &y);
    ans = max(ans, x + y);
  }
  inline bool operator<(const node &p) const {
    return x == p.x ? y < p.y : x < p.x;
  }
} a[maxn];
inline void work() {
  int n;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) a[i].read();
  printf("%lld\n", ans);
  return;
}
