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.

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