Uses crt;
Var
    ab,cd:array[1..1000] of integer;
    a,b,c,d: real;
    i1,i2,n,v1,v2: integer;
Begin
    repeat
        clrscr;
        write('Nhap a,b,c,d: '); readln(a,b,c,d);
    until(a<b) and (c<d);
    n:=round(a)-1; v1:=round(b)-round(a)+1;
    for i1:=1 to v1 do ab[i1]:=n+i1;
    n:=round(c)-1; v2:=round(d)-round(c)+1;
    for i2:=1 to v2 do cd[i2]:=n+i2;
    n:=0;
    for i1:=1 to v1 do
        begin
        for i2:=1 to v2 do
            begin
            if cd[i2]=ab[i1] then n:=1;
            end
        end;
    if n=0 then writeln('NO') else writeln('YES');
    readln;
End.

Hoặc:

Uses crt;
Var
    a,b,c,d: real;
Begin
    repeat
        clrscr;
        write('Nhap a,b,c,d: '); readln(a,b,c,d);
    until(a<b) and (c<d);
    if b>=c then writeln('YES') else writeln('NO');
    readln;
End.

uses crt;
var a,b,c,d:longint;
begin
clrscr;
   readln(a,b,c,d);
   if c<=b then write('YES') else write('NO');
readln
end.