#include <bits/stdc++.h>

typedef long long ll;
#define rep(i, b) for(int i = 0; i < b; i++)
#define repi(i, a, b) for(int i = a; i < b; i++)
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define MAX_V 1001
#define MAX_E 401
#define MOD 1000000007
#define EPS 1e-5
#define INF INT_MAX
#define PI 3.141
inline ll toll(std::string s) { ll v; std::istringstream sin(s); sin >> v; return v; }
template<class T> inline std::string toString(T x) { std::ostringstream sout; sout << x; return sout.str(); }
using namespace std;
typedef pair<int, int> pii;

int main()
{
	int N;
	ll ans = 0;

	cin >> N;
	rep(i, N)
	{
		int H, M, h, m;
		char c;
		cin >> H >> c >> M >> h >> c >> m;
		
		if (H == h)
		{
			if (M >= m)
			{
				ans += 60 * 23 + (60 - M) + m;
			}
			else{
				ans += m - M;
			}
		}
		else if (H > h)
		{
			if (M >= m)
			{
				ans += 60 * (24 - H + h - 1) + (60 - M) + m;
			}
			else{
				ans += 60 * (24 - H + h) + (m - M);
			}
		}
		else{
			if (M >= m)
			{
				ans += 60 * (h - H - 1) + (60 - M) + m;
			}
			else{
				ans += 60 * (h - H) + (m - M);
			}
		}
	}
	cout << ans << endl;
	return 0;
}