//Mihai Priboi

#include <stdio.h>
#include <stdlib.h>

int cautbin( int x ) {
  int r, pas;
  pas = 1 << 28;
  r = 0;
  while( pas ) {
    if( nr_zero(r + pas) < x )
      r += pas;
    pas /= 2;
  }
  return r + 1;
}

int nr_zero( int n ) {
  int nr;
  nr = 0;
  while( n >= 5 ){
    nr += n / 5;
    n /= 5;
  }
  return nr;
}

int main() {
  FILE *fin, *fout;
  int n, p;
  fin = fopen( "fact.in", "r" );
  fscanf( fin, "%d", &p );
  fclose( fin );
  fout = fopen( "fact.out", "w" );
  n = cautbin(p);
  fprintf( fout, "%d", nr_zero(n) == p ? n : -1 );
  fclose( fout );
  return 0;
}