SONN Pascal

var d:array[-100..100] of longint;
    i,x,n:longint
    ;
procedure nhap_va_dem;
var i:longint;
begin
    readln(n);
    for i:=1 to n do
    begin
        read(x);
        inc(d[x]);
    end;
end;

procedure giai;
var i:longint;
begin
    for i:=-100 to 100 do
        if d[i]=1 then
        begin
            write(i);
            exit;
        end;
    write('khong');
end;

begin
    assign(input,'sonn.inp');reset(input);
    assign(output,'sonn.out');rewrite(output);
    nhap_va_dem;
    giai;
end.