CHEAT - Chơi bi-a 1 lỗ
Tác giả: flashmt
Ngôn ngữ: Pascal
uses math;
var l,r:array[0..100000] of longint;
n,i,x,m:longint;
begin
read(n);
for i:=1 to n do r[i]:=i+1;
for i:=2 to n do l[i]:=i-1;
m:=0;
for i:=1 to n do
begin
read(x);
if r[x]<m then
begin
writeln('YES');
halt;
end;
r[l[x]]:=r[x];
l[r[x]]:=l[x];
m:=max(m,x);
end;
writeln('NO');
end.