#include <fstream>
#include <iostream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
   int main()
  {
     float n,p=0;
     in>>n;
     if(n==0)
     {
       out<<"1";
       return 0;

     }
    int k=1;
     for(int i=5;k<=n;i=i+5)
     {
        p=p+5;
        k++;
     }
     out<<p;

}