#include <iostream>

#include <cstdio>

#include <cstring>

using namespace std;

double totsum,totnum,k;

char s[];

int n;

double get()

{

    if (s[]=='A')

    {

        if (s[]==) return ;

        else return 3.7;

    }

    if (s[]=='B')

    {

        if (s[]==) return ;

        else if (s[]=='+') return 3.3;

        else return 2.7;

    }

    if (s[]=='C')

    {

        if (s[]==) return ;

        else if (s[]=='+') return 2.3;

        else return 1.7;

    }

    if (s[]=='D')

    {

        if (s[]==) return 1.3;

        else return ;

    }

    if (s[]=='F') return ;

    return -;

}

int main()

{

    while (scanf("%d",&n)!=EOF)

    {

        totsum=totnum=;

        while (n--)

        {

            scanf("%lf%s",&k,s);

            double tep=get(); //cout<<" this is : "<<tep<<endl;

            if (tep<) continue;

            totnum+=k;

            totsum+=k*tep;

        }

        if (totnum==) printf("0.00\n");

            else printf("%.2f\n",totsum/totnum);

    }

    return ;

}