#include <iostream>
#include <iomanip>
#include <string>
#include <map>
using namespace std;
map<string, double> m = {
{"A+", 4.3}, {"A0", 4.0}, {"A-", 3.7},
{"B+", 3.3}, {"B0", 3.0}, {"B-", 2.7},
{"C+", 2.3}, {"C0", 2.0}, {"C-", 1.7},
{"D+", 1.3}, {"D0", 1.0}, {"D-", 0.7},
{"F", 0.0}
};
void solve(void) {
int n; cin >> n;
int credit = 0;
double sum = 0;
for (int i=0; i<n; i++) {
string a, c; int b; cin >> a >> b >> c;
sum += b * m[c];
credit += b;
}
sum += 1e-9;
cout << fixed << setprecision(2) << sum / credit;
}
int main(void) {
ios::sync_with_stdio(false);
cin.tie(nullptr);
solve();
return 0;
}