#include<cstdio>
#include<iostream>
#include<cstring>
#define ll long long
using namespace std;
const int ma=1e5+10;
int main()
{
ll a[5];
ll s=0;
char str[ma];
cin>>a[1]>>a[2]>>a[3]>>a[4];
cin>>str;
ll len=strlen(str);
for(int i=0;i<len;i++)
{
int t=str[i]-'0';
s+=a[t];
}
cout<<s<<endl;
return 0;
}