#include<bits/stdc++.h>
using namespace std;
int main()
{
int N,i,a,s,d,f,g,h=0;
cin>>N;
for(i=1;i<=N;i++){
    a=i%10;
    s=i%100/10;
    d=i%1000/100;
    f=i%10000/1000;
    g=i%100000/10000;
    if(i%5==0&&(a==5||s==5||d==5||f==5||g==5))
        h++;
}
cout<<h;
return 0;
}
/**************************************************************
	Problem: 1057
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/