#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,sum=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		int m[5]={i/10000,i/1000%10,i/100%10,i/10%10,i%10};
		if(i%5==0&&(m[0]==5||m[1]==5||m[2]==5||m[3]==5||m[4]==5))sum++;
	}
	cout<<sum;
	return 0;
}

/**************************************************************
	Problem: 1057
	User: zhouhongyi
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/