#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  long long n, cnt1 = 0, cnt2 = 0, l, r;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> l >> r;
    cnt1 += l;
    cnt2 += r;
  }
  cout << min(cnt1, n - cnt1) + min(cnt2, n - cnt2);
}
