#include <bits/stdc++.h>
using namespace std;
int main()
{
	int sum=0;
	int g,s,b,q,w;
	int n;
	cin>>n;
for(int i=1;i<=n;i++){
	g=i/1%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 )){
		sum++;
	}
	
}
cout<<sum<<endl;
return 0;

}

/**************************************************************
	Problem: 1057
	User: mc002
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2072 kb
****************************************************************/