var p,k,i,j,n:longint;
        f,g:text;
begin
        assign(f,'fact.in');
        reset(f);
        read(f,p);
        close(f);

        i:=0;
        k:=1;
        repeat
                inc(i);
                k:=k*i;

                n:=k;
                j:=0;
                repeat
                        if n mod 10=0 then inc(j);
                        n:=n div 10;
                        until (n=0)or(n mod 10>0);
        until j=p;

        assign(g,'fact.out');
        rewrite(g);
        write(g,i);
        close(g);
end.