#include<cstdio>
#include<cmath>
#include<algorithm>

using namespace std;
int main()
{

	freopen("sunny.in", "r", stdin);
	freopen("sunny.out", "w", stdout);
	int n;
	int h1, h2, m1, m2, u;
	double t, e=0;
	char c1, c2;
	scanf("%d", &n);

	for(int i=0; i<n; i++)
	{
		scanf("%d:%d %cm %d:%d %cm %d", &h1, &m1, &c1, &h2, &m2, &c2, &u);
		if(c1=='a' && c2=='p')
		{
			t = h2-h1+12+((double)m2-m1)/60;
			//printf("%d:%d %cm %d:%d %cm %d %lf", h1, m1, c1, h2, m2, c2, u, t);
		}
		else
		{
			t = h2-h1+((double)m2-m1)/60;
			//printf("%d:%d %cm %d:%d %cm %d %lf", h1, m1, c1, h2, m2, c2, u, t);
		}

		e += (double)sqrt((double)u)*u*t;
	}

	printf("%.3lf\n", e);

	return 0;
}