uses crt;
var a, b, c, d, e: integer;
function max(x, y: integer): integer;
begin
if x>=y then
max:=x
else
max:=y;
end;
begin
clrscr;
write ('nhap so thu nhat: '); readln (a);
write ('nhap so thu hai: '); readln (b);
write ('nhap so thu ba: '); readln (c);
write ('nhap so thu tu: '); readln (d);
write ('so lon nhat la: ',max(max(max(a, b), c), d));
readln;
end.
end.