
theorem Th14:
  for n being non zero Nat,
      x being Integer,
      k,l being Nat
  st k < n & l < n & x,k are_congruent_mod n & x,l are_congruent_mod n
  holds k = l
proof
let n be non zero Nat,
    x be Integer,
    k,l be Nat;
assume A1: k < n & l < n &
   x,k are_congruent_mod n & x,l are_congruent_mod n;
hence k = x mod n by Th12 .= l by A1,Th12;
end;
