#include <iostream>
#include<utility>
#include <vector>
#include <map>
#include<string>
#include<queue>
#include<math.h>
#define pb push_back
#define all(x) begin(x),end(x)
#define ll long long
#define P pair<int,int>
#define lP pait<ll,ll>
using namespace std;
int main() {
    int n,cnt=0;
    cin>>n;
    for(int i=0;i<n;i++){
        int a,b,c,d;
        char e,f;
        cin>>a>>e>>b>>c>>f>>d;
        if(a>c){
            if(b>=d) cnt+=60*((24-a)+c-1)+60-b+d;
            else if(b<d) cnt+=60*((24-a)+c)+d-b;
        }
        else if(a==c){
            if(d>=b) cnt+=d-b;
            else if(d<b)  cnt+=60*24-b;
        }
        else{
            if(d>=b) cnt+=60*(c-a)+d-b;
            else if(d<b)  cnt+=60*(c-a-1)+60-b+d;
        }
    }
    cout<<cnt<<endl;
    return 0;
}