KPLANK

const
    finp = '';
    fout = '';
    maxn = 1000000 + 10;

var
    fi,fo: text;
    a: array[0..maxn] of longint;
    next,previous,stack: array[0..maxn] of longint;
    n,kq,top: longint;

procedure mofile;
begin
    assign(fi,finp);
    reset(fi);
    assign(fo,fout);
    rewrite(fo);
end;

procedure dongfile;
begin
    close(fi);
    close(fo);
end;

procedure push(i: longint);
begin
    inc(top);
    stack[top] := i;
end;

procedure nhap;
var
    i: longint;
begin
    readln(fi,n);
    for i := 1 to n do
    begin
        read(fi,a[i]);
        next[i] := i;
        previous[i] := i;
    end;
end;

procedure tim;
var
    i,dodaihientai: longint;
begin
    kq := 0;
    a[0] := -1;
    a[n + 1] := -1;

    top := 0;
    for i := 1 to n + 1 do
    begin
        while (top > 0) and (a[i] < a[stack[top]]) do
        begin
            next[stack[top]] := i;
            dec(top);
        end;
        push(i);
    end;

    top := 0;
    for i := n downto 0 do
    begin
        while (top > 0) and (a[i] < a[stack[top]]) do
        begin
            previous[stack[top]] := i;
            dec(top);
        end;
        push(i);
    end;

    for i := 1 to n do
    begin
        dodaihientai := (next[i] - ord(i <> next[i])) - (previous[i] + ord(i <> next[i])) + 1;
        if (dodaihientai >= a[i]) and (a[i] > kq) then kq := a[i];
    end;
end;

procedure xuat;
begin
    writeln(fo,kq);
end;

BEGIN
    mofile;
    nhap;
    tim;
    xuat;
    dongfile;
END.