#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int left[n], right[n];
  int leftOpen = 0, leftClose = 0, rightOpen = 0, rightClose = 0;
  for (int i = 0; i < n; i++) {
    cin >> left[i];
    cin >> right[i];
    if (left[i])
      leftOpen += 1;
    else
      leftClose += 1;
    if (right[i])
      rightOpen += 1;
    else
      rightClose += 1;
  }
  int minCount = 0;
  if (leftOpen > leftClose)
    minCount += leftClose;
  else
    minCount += leftOpen;
  if (rightOpen > rightClose)
    minCount += rightClose;
  else
    minCount += rightOpen;
  cout << minCount << endl;
}
