#include <iostream>
using namespace std;
int main()
{
int C ;
double x ,count = 0 ;
char s = 'S' , m = 'M' , L ;
cin >> C >> L ;
for (int i = 0; i < 12 * 12; i ++ )
{
cin >> x ;
if(C == i) count += x , C += 12; //不需要额外数组开销
}
if(L == s) cout << count <<endl;
if(L == m) printf("%.1lf",count / 12);
return 0;
}