431A - Black Square

using namespace std;
using vi = vector<int>;
int main(void)
{
    int ans = 0;
    vi cost(4, 0);
    string s;
    for (auto &x : cost)
        cin >> x;
    cin >> s;
    for (auto c : s)
        ans += cost[c - '0' - 1];
    cout << ans << endl;
    return 0;
}