/*
 * main.cpp
 *
 *  Created on: Feb 17, 2013
 *      Author: krassi
 */
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;
typedef unsigned uint;

int read_time() {
	int h, m;
	char c;
	char ap[2];
	cin >> h >> c >> m >> ap;
	if (ap[0] == 'a' && h == 12) {
		h = 0;
	} else if (ap[0] == 'p' && h != 12) {
		h += 12;
	}
	return 60 * h + m;
}

int main(int argc, char **argv) {
	//freopen("sunny.in", "r", stdin);
	//freopen("sunny.out", "w", stdout);

	int n; scanf("%d", &n);
	double sum = 0;
	for (int i = 0; i < n; ++i) {
		int t1 = read_time();
		int t2 = read_time();
		int u; cin >> u;

		double t = t2 - t1;
		t /= 60;
		double uuu = sqrt(u) * u;
		sum += t * uuu;
	}
	printf("%.3lf\n", sum);
	return 0;
}