#include <fstream>

using namespace std;

ifstream fin( "fact.in" );
ofstream fout( "fact.out" );

int K;

int main()
{
  fin >> K;

  if( K == 0 )
  {
    fout << "1\n";

    return 0;
  }

  long long nr = 0, aux;
  int nr5 = 0;

  while( nr5 < K )
  {
    nr += 1LL * 5;
    aux = nr;
    while( aux % 5 == 0 )
    {
      ++nr5;
      aux /= 5;
    }
  }

  fout << nr << '\n';

  return 0;
}