#include <iostream>

#include <vector>

#include <algorithm>

using namespace std;

int main(){

	vector<int> a(4);

	cin >> a[0] >> a[1]>>a[2]>>a[3];

	string str;

	cin >> str;

	int res = 0;

	for(int i = 0 ; i < str.length(); ++ i) res+=a[str[i]-'0'-1];

	cout<<res<<endl;

}