#include <stdio.h>
#include <stdlib.h>

int main()
{
    long p=0,n=0,c,r;
    FILE *f=fopen("fact.in","r");
    FILE *g=fopen("fact.out","w");

    fscanf(f,"%d",&p);

    c=p/5;
    r=p%5;

    if((c-1)==r)
    {
        fprintf(g,"-1\n");
    }
    else if(p==0)
    {
        fprintf(g,"1\n");
    }
    else if(r==0)
    {
        fprintf(g,"%ld\n",(p-(c-1))*5);
    }
    else
    {
        fprintf(g,"%ld\n",(p-c)*5);
    }

    fclose(f);
    fclose(g);

    return 0;
}