#include <bits/stdc++.h> 
using namespace std;
#include <ios>
#include <iomanip>
#include <iostream>
#include <string>
#include <algorithm>

int main(){
  double count=0;
  int number;
  cin >> number;
  for(int i=0; i<number; i++){
  stringstream ss;
  string str;
  cin >> str;
  int a, b;
  ss << str;
  ss >> a;
  ss.ignore();
  ss >> b;
  stringstream ss2;
  string str2;
  cin >> str2;
  int d, c;
  ss2 << str2;
  ss2 >> c;
  ss2.ignore();
  ss2 >> d;
  double e;
  double f;
    if(a>=12&&c<a){
      e=(23-a)+c;
    }
    else if(a==c&&d<b){
    e=23;
    }
    else if(a==c){
      e=fabs(a-c);
    }
    else{
      e=fabs(a-c)-1;
    }
    	if(d<b||a!=c){
     	 f=fabs(60-b+d);
        }
    	else if(b<d){
     	 f=fabs(b-d);
    	}
 		 count += e*60+f;
  }	
  cout << count;
}