#include <bits/stdc++.h>
using namespace std;
const int N = 100100;
long long ans = 0;
int n;
int a[N], b[N];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i] >> b[i];
  }
  sort(a + 1, a + n + 1);
  sort(b + 1, b + n + 1);
  ans = n;
  for (int i = 1; i <= n; i++) ans += max(a[i], b[i]);
  cout << ans;
}
