#include<iostream>
#include<fstream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
long long n,h1,m1,h2,m2,t;
string s1,s2;
char c;
double ans;
double length(long long h1, long long m1, long long s1, long long h2, long long m2, long long s2)
{
    double ans=0;
    if(h1==12) h1=0;
    if(h2==12) h2=0;
    if(s1==1)
    {
        if(s2==1)
        {
            ans=h2*60+m2-h1*60-m1;
            ans=ans/60.0;
            return ans;
        }
        else if(s2==2)
        {
            ans=h2*60+m2-h1*60-m1+12*60;
            ans=ans/60.0;
            return ans;
        }
    }
    else if(s1==2)
    {
        if(s2==2)
        {
            ans=h2*60+m2-h1*60-m1;
            ans=ans/60.0;
            return ans;
        }
    }
}
int main()
{
    ifstream cin;
    cin.open("sunny.in");
	cin>>n;
	for(int i=1; i<=n; i++)
	{
	    cin>>h1>>c>>m1>>s1;
	    cin>>h2>>c>>m2>>s2;
	    cin>>t;
	    ans+=(double)(length(h1,m1,(s1=="am"?1:2),h2,m2,(s2=="am"?1:2))*t)*sqrt(t);
	}
	cin.close();
	freopen("sunny.out","w",stdout);
	printf("%.3lf\n",ans);
	return 0;
}