#include <iostream>

using namespace std;
const int N = 30;
int q[N];

int main(){
    int x,k = -1,res = 0;
    while(cin >> x)
        if(x > 0) q[++k] = x;
    int flag = 1;
    for(int i = 0;i <= k;i++){
        if(q[i] == 2){
            if(flag == 1) res += q[i];
            else res += q[i] * flag;
            flag++; 
        }else if(q[i] == 1){
            flag = 1;
            res += 1;
        }
    }

    cout << res << endl;
    return 0;
}