include<iostream>

include<cmath>

using namespace std; int main(){ int a,b,c,d,g,n,q; cin>>a; b=a/5; if(a%10==5 or a%10==0){ cout<<b; } if(a%10==9 or a%10==7 or a%10==4 or a%10==2 or a%10==1){ cout<<b+2; } if(a%10==8 or a%10==3 or a%10==6){ cout<<b+1; } }