#include<bits/stdc++.h> using namespace std; int main(){ int t,h1,m1,h2,m2,t1,t2,d; scanf("%d",&t); scanf("%d:%d",&h1,&m1); scanf("%d:%d",&h2,&m2); t1=h1*60+m1; t2=h2*60+m2; d=ceil(1.0*t/(t2-t1)); printf("%d",d); return 0; }