#include <stdio.h>
#include <stdlib.h>
FILE *in,*out;long n,P;
int main()
{
   in=fopen("fact.in","r");
   out=fopen("fact.out","w");
   fscanf(in,"%ld",&P);
if(P*5>=0)
fprintf(out,"%ld",P*5);
else
fprintf(out,"-1");


   fclose(in);fclose(out);
    return 0;
}