uses crt;
var a,b,c,d:integer;
function max(x,y:integer):integer;
begin
if x<y then max:=y
else max:=x;
end;
begin
clrscr;
write('a='); readln(a);
write('b='); readln(b);
write('c='); readln(c);
write('d='); readln(d);
writeln(max(a,max(b,max(c,d))));
readln;
end.