#include <bits/stdc++.h>
using namespace std;
    
int main (){

  #ifndef ONLINE_JUDGE
    freopen("SuhaibSawalha1","r",stdin);
  #endif

  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int n;
  cin >> n;
  bool ok = 0, ok2 = 0;
  int ans = 0;
  while (n--) {
    int x;
    cin >> x;
    ok |= x == 0;
    ok2 |= x == 1;
    if (ok && ok2) {
      ++ans;
      ok = ok2 = 0;
    }
  }
  cout << ans;

  return 0;
}