#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cstring>
#include <cctype>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <stdio.h>
#include <string.h>
#include <cstdlib>
#include <math.h>
#include <bitset>
#include <iterator>
#include <iomanip>
#include <sstream>
#define INF 2000000000
using namespace std;
int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
#define sym cout<<"---------"<<endl;
#define ll long long
#define PL pair<long long, long long>
#define P pair<int,int>
#define mk make_pair
#define en endl
#define WHITE 0
#define BLACK 2
#define GRAY 1
#define RE return 0
#define int ll

int done[11];

signed main(){
  int n;
  cin>>n;
  int ans=0;
  for(int i=0; i<n; i++){
    int h,m,H,M;
    char ch;
    cin>>h>>ch>>m;
    cin>>H>>ch>>M;
  
    if(H<=h) {
      if(H==h){
        if(M>=m) ans+=M-m;
        else ans+=23*60+60-(m-M);
        continue;
      }
      ans+=(24-h-1)*60+60-m;
      ans+=H*60+M;
    }else if(M<m){
      ans+=(H-h-1)*60+(60-m+M);
    }else ans+=(H-h)*60+M-m;

  }
  cout<<ans<<en;
}