#include<bits/stdc++.h>
using namespace std;
int n,i=1,m,g,s,b,q,w;
int main(){
	cin>>n;
	while(i<=n){ 
		g=i%10;
		s=i/10%10;
		b=i/100%10;
		q=i/1000%10;
		w=i/10000;
		if(i%5==0&&(g==5||s==5||b==5||q==5||w==5)) m+=1;
		i++;
	}
	cout<<m;
	return 0;
}
/**************************************************************
	Problem: 1057
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/