#include<iostream> #include<cmath> using namespace std; int main(){ int m,a,b,c,d,s; cin>>m; scanf("%d:%d",&a,&b); scanf("%d:%d",&c,&d); s=(c-a)*60+d-b; if(m%s==0)cout<<m/s; else if(m%s!=0)cout<<m/s+1; return 0; }