#include<stdio.h>
FILE *f=fopen("fact.in","r"),*g=fopen("fact.out","w");
int main()
{
 long int n,n5=0,i,nr;
 fscanf(f,"%ld",&n);
 if(n==0) {fprintf(g,"1");return 0;}
 for(i=1;n5<n;i++)
 {
   n5++;
   if(!(i%5))
   {
     nr=i;
     while(!(nr%5)) {nr/=5;n5++;}
   }

 }
 if(n5==n) fprintf(g,"%ld",(i-1)*5);
 else fprintf(g,"-1");
 return 0;
}