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;
        n:=1;
        j:=0;
        repeat
                n:=n*10;
                inc(j);
                until j=p;
        repeat
                inc(i);
                k:=k*i;

                until k mod n=0;

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