#include<iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{int p=0,i=0,c=0,a=0;
 f>>p;
 for(i=5,c=0;c!=p;i+=5)
 {a=i;
  while(a)
  {if(a%5==0)
      c++;
   else
	  break;
   a/=5;
  }
 }
 g<<i-5;
 return 0;
}