#include <stdio.h>
FILE *f,*g;
int main()
{long int p,n,d;
unsigned int k,i;
f=fopen("fact.in","r");
fclose(f);
fscanf(f,"%ld",&p);
g=fopen("fact.out","w");
n=0;
i=0;
if(p==0){ fprintf(g,"1");
	  i=1;}
if(p<0) { fprintf(g,"-1");i=1;}

if(p>0) while(p>0){n=n+5;
		   p--;
		   d=n/5;
		   k=1;
		   while(k==1)
			 if(d%5==0) {p--;d=d/5;}
			     else k=0;
		  }

 if(i==0) fprintf(g,"%ld",n);
fclose(g);
return 0;
}