#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define repp(i, m, n) for (int i = (int)m; i < (int)n; i++)
#define all(v) begin(v), end(v)
using namespace std;
using ll = long long int;

int main() {
    // 入力
    int N;
    cin >> N;

    // 合計睡眠時間
    int sleep = 0;
    rep(i, N) {
        // 入力
        int H, M, h, m;
        cin >> H;
        cin.ignore();
        cin >> M >> h;
        cin.ignore();
        cin >> m;

        while (H != h || M != m) {
            M++;
            if (M == 60) { M = 0; H++; }
            if (H == 24) { H = 0; }
            sleep++;
        }
    }

    // 出力
    cout << sleep << endl;
}