#include<bits/stdc++.h>
#define int long long
#define rep(i,x,y) for(int i=x;i<=y;i++)
#define pre(i,x,y) for(int i=x;i>=y;i--)
using namespace std;
const int N=2e5+10,INF=0x3f3f3f3f,mod=1e9+7;
inline int read() {
int x=0,f=1;
char ch=getchar();
while(ch<'0'||ch>'9')f=((ch=='-')?-1:f),ch=getchar();
while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar();
return x*f;
}
void solve(){
int a=read(),ta=read();
int b=read(),tb=read();
int h,m;
scanf("%lld:%lld",&h,&m);
int t1=h*60+m,t2=t1+ta;
//cout<<t1-tb<<" "<<t2<<endl;
int bt=5*60;
int ans=0;
for(int i=bt;i<=23*60+59;i+=b){
//cout<<i<<endl;
if(t1-tb<i&&i<t2)ans++;
}
cout<<ans;
}
signed main(){
int T=1;
//T=read();
while(T--)solve();
return 0;
}
/*
10 30
10 35
05:35
*/
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