#define _USE_MATH_DEFINES
#include <iostream>
#include <iomanip>
#include <map>
#include <stack>
#include <vector>
#include <string>
#include <cmath>
using namespace std;
const int MOD = 1e9 + 7;

int solve(){
    int h, m, hh, mm;
    char c;
    cin >> h >> c >> m >> hh >> c >> mm;

    int ret = 0;
    if(h > hh){
        ret += (24 - h - 1) * 60;
        ret += 60 - m;
        ret += hh * 60;
        ret += mm;
    }else if(h == hh){
        if(m > mm){
            ret += 23 * 60;
            ret += 60 - (m - mm);
        }else{
            ret += mm - m;
        }
    }else{
        if(m < mm){
            ret += (hh - h) * 60;
            ret += mm - m;
        }else{
            ret += (hh - h - 1) * 60;
            ret += 60 - (m - mm);
        }
    }
    return ret;
}
int main(){
    int n;
    cin >> n;
    int ans = 0;
    for(int i = 0; i < n; i++){
        ans += solve();
    }
    cout << ans << endl;
}