theorem
 for I being set, Y being non empty set
 for p being Y-valued I-defined Function
  ex s being Y-valued ManySortedSet of I st p c= s
 proof
  let I be set, Y being non empty set;
  let p be Y-valued I-defined Function;
   set h = the Y-valued ManySortedSet of I;
  take h+*p;
  thus p c= h+*p by FUNCT_4:25;
 end;
