Объяснение:
var i,pos,neg:integer;
z:array[1..4]of integer;
begin
for i:=1 to 4 do
begin
read(z[i]);
end;
for i:=1 to 4 do
begin
if (z[i] < 0) then
neg:=neg+1;
if (z[i] > 0) then
pos:=pos+1;
end;
if (pos>0) and (neg>0) then
write('YES')
else
write('NO');
end.
