err.pl0

const 
  m = 7, n = 85
var 
  i,x,y,z,q,r;
procedure multiply; 
var 
  a,b;
begin 
  a := u; b := y; z := 0
  while b > 0 do
  begin 
    if odd b do z := z+a; 
    a := 2a; b := b/2; 
  end 
end;

procedure divide
var w;
const
   two = 2, three := 3;
begin 
  r = x; q := 0; w := y; 
  while w <= r do w := 2*w;
  while w > y
  begin q := (2*q; w := w/2); 
    if w <= r then 
    begin 
      r := r-w 
      q := q+1;
    end 
  end 
end;

procedure gcd;
var 
  f,g;
begin 
  f := x; g := y 
  while f # g do
    begin if f<g then g := g-f; 
          if g<f then f := f-g; 
    end;
  z := f;
end;

begin 
  i:=1;
  while i#0 do
  begin
    x := m; y := n; call multiply;
    x := 25; y := 3; call divide; 
    x := 84; y := 36; call gcd; 
    call x;
    x := gcd;
    i:=i-1;
  end;
end.