#define _USE_MATH_DEFINES
#include<stdio.h>
#include<string>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include<iomanip>

//#include<bits/stdc++.h>



using namespace std;




int main() {

	int n;
	cin>>n;
	int ans=0;
	for(int i=0;i<n;i++){
		int h,m,a,b;
		char r;
		cin>>h;cin>>r;
		cin>>m;
		cin>>a>>r>>b;
		a*=60;
		a+=b;
		h*=60;
		h+=m;
		if(a>=h){
			a-=h;
		}
		else a+=60*24-h;
		ans+=a;
	}

	cout<<ans<<endl;
	return 0;
}