[Aristarh Dark]

так чтоль?

Код:

const
  N = 50;
  M = 100;

type
  TMatrix = array [1..N,1..M] of integer;

procedure ChangeElements(var aMatrix:TMatrix;aMessage:string);
var
  i,j,count:integer;
begin
  count:=0;
  for i:=1 to N do
    for j:=1 to M do
      if aMatrix[i,j]<0 then
        begin
          aMatrix[i,j]:=abs(aMatrix[i,j]);
          inc(count);
        end;
  if count=M*N then
    WriteLn(aMessage);
end;