#include <stdio.h>
long p,s,n,i;
FILE *f,*g;


int main()
{ f=fopen ("fact.in","r");
  g=fopen ("fact.out","w");
  fscanf (f,"%ld",&p);
 for (i=1;i<=p;i++) {n=n+5;
                     if (s==5) n=n-5;
                     s=s+1;}
if (p==0) fprintf (g,"1");
      else if (p<0) fprintf (g,"-1");
            else fprintf (g,"%ld",n);


fclose(f);
fclose(g);
    return 0;
}