#include<stdio.h>
FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");

int main()
{
	long long  v=0,j,p,i,k=0;
	 
	fscanf(f,"%lld",&p);
	
	if(p==0) fprintf(g,"1\n");
	else {
	for(i=1;i<=p;i++)
	{
		j=i;
		v+=5;
		k++;
		           		
		 while(j%5==0)
		      {
                 j=j/5;
				 k++;
			   }	
     if(k>=p) break;
	 }
	
	 if(k==p) fprintf(g,"%lld\n",v);
	 else fprintf(g,"-1\n");
	}
	 fclose(f);
	 fclose(g);
	 return 0;
}