#include <iostream>
using namespace std;
int main(){
	int i=1,n,g,s,b,q,w,c=0;
	cin>>n;
	for(i=1;i<=n;i++){
		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))
			 c++; 
	}
		cout<<c<<endl;
}
/**************************************************************
	Problem: 1057
	User: fandaohan
	Language: C++
	Result: Accepted
	Time:21 ms
	Memory:2072 kb
****************************************************************/