reserve G for non empty DTConstrStr,
  s for Symbol of G,
  n,m for String of G;
reserve n1,n2,n3 for String of G;
reserve a,b,c for set,
  D for non empty set,
  d for Element of D;
reserve R for Relation,
  x,y for set;

theorem
  R c= R[*]
proof
  let x,y be object;
A1: len <*x,y*> = 2 by FINSEQ_1:44;
A2: <*x,y*>.2 = y;
  assume
A3: [x,y] in R;
  then
A4: y in field R by RELAT_1:15;
A5: <*x,y*>.1 = x;
A6: now
    let i be Nat such that
A7: i >= 1 and
A8: i < 2;
    1+1 = 2;
    then i <= 1 by A8,NAT_1:13;
    then i = 1 by A7,XXREAL_0:1;
    hence [<*x,y*>.i,<*x,y*>.(i+1)] in R by A3;
  end;
  x in field R by A3,RELAT_1:15;
  hence thesis by A4,A1,A5,A2,A6,FINSEQ_1:def 17;
end;
