123122111111

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e6 + 5;
int a[N];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, cnt0 = 0, cnt2 = 0, k = 0, t = 0, k2 = 0, t0 = 0;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        if (a[i] == 0)
            cnt0++;
        if (a[i] == 2)
            cnt2++;
    }
    for (int i = 1; i <= cnt0; i++) {
        if (a[i] != 0) {
            k++;
        }
        if (a[i] == 2)
            k2++;
    }
    for (int i = n - cnt2 + 1; i <= n; i++) {
        if (a[i] != 2) {
            t++;
        }
        if (a[i] == 0)
            t0++;
    }
    cout << k + t - min(k2, t0);
    return 0;
}