#include <stdio.h>
int main()
{
int p,k,i,z;
long int n,emi;
FILE *fin, *fout;
fin=fopen("fact.in","r");
scanf("%d",&p);
n=1;
i=1;
z=0;
while (z!=p && n<=1000000)
 {
 n*=i;//calculeaza factorialul
 i++;
 z=0;//indicator pt nr de 0-uri ale lui n
 emi=n;//salvez valoarea lui n pt a nu se pierde
 k=0;
  while (k==0)
      {
      k=emi%10;
      emi=emi/10;
      z++;
      }
  };
  fclose(fin);
  fout=fopen("fact.out","w");
  if (z==p) fprintf(fout,"%d",i);
  else fprintf(fout,"-1");
  fclose(fout);
  return 0;
  }