#include <bits/stdc++.h>
using namespace std;
int main() {
int a[8], cnt1 = 0;
    for(int i = 0; i < 8; i++)
    {
        cin >> a[i];
        if(a[i] == 1) cnt1++;
    }
    int ans = 0;
    if(cnt1 > 4)
    {
        ans = (cnt1 - 4) / 2;
    }
    else if(cnt1 < 4)
    {
        ans = (4 - cnt1) / 2;
    }
    cout << ans;
    return 0;
}