//4.17
var
  x: array[1..4,1..4] of real;
  max: real;
  i, j: integer;

begin
  writeln('Vvedite matricu 4x4:');
  
  
  max := -30000;
  
  for i := 1 to 4 do
    for j := 1 to 4 do
      begin
        read(x[i,j]);
        if (i = j)AND(x[i,j] < 0)AND(x[i,j] > max) then
          max := x[i,j];
      end;
  if max = -30000
    then writeln('Netu otricatelnih elementov.')
    else
    writeln('Naibolshij otricatelnij element glavnoj diagonali matrici = ', max);
end.