reserve X for set;
reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve r,s for Real;
reserve p,p1,p2,p3 for Prime;
reserve z for Complex;

theorem Th33:
  i*n,n are_congruent_mod n
  proof
A1: i*n,0 are_congruent_mod n;
    0,n are_congruent_mod n by INT_1:12;
    hence thesis by A1,INT_1:15;
  end;
