\programVariables{
  int n,i,r;
}
\problem{
  \forall int nl; (0 <= nl) ->
    {n:=nl}
    \<{ i=0;
        r=0;
        while (i < n) {
          i++;
          r = r + (i*i*i);
        }
    }\> 4*r = nl*nl*(nl+1)*(nl+1) )
}