uses crt;
var max,a,b,c,d,m:integer;
s:real;
begin
clrscr;
writeln('Nhap a,b,c,d');readln(a,b,c,d);
s:=sqr(a-b)/(sqr(c)-d);
writeln('ket qua: ',s:2:3);
max:=a;
if b>max then max:=b;
if c> max then max:=c;
if d>max then max:=d;
writeln('so lon nhat la: ',max);
if (a>0) or (b>0) or (c>0) or (d>0) then
m:=a*b*c*d;
writeln('m=',m);
readln
end.