puloGatoPj.cpp

#include <bits/stdc++.h>
using namespace std;

int main(){

    int c; cin >> c;

    vector<int> v(c+5,0), res(c+5, -1);

    for(int i=1; i<=c; i++) cin >> v[i];

    res[1] = 0;

    for(int i=1; i<c; i++){

        if(v[i] == 0) continue;
        if(res[i] == -1) continue;

        if(v[i+1] == 1 and res[i+1] == -1) res[i+1] = res[i] + 1;
        if(v[i+2] == 1 and res[i+2] == -1) res[i+2] = res[i] + 1;
    }

    cout << res[c] << endl;
    return 0;
}