Помогите пожалуйста :((( Даны шесть монет, из которых одна фальшивая. Фальшивая монета...

Var
    a, real_coin: array[1..6] of integer;
    forged_coin, i: integer;

begin
    for i := 1 to 6 do
        a[i] := 10;
    forged_coin := random(6);
    a[forged_coin] := random(4) + 8;
    writeln(forged_coin);

    for i := 1 to 6 do
        write(a[i], ' ');
    writeln;

    forged_coin := 0;
    if a[1] + a[2] = a[3] + a[4] then begin
        real_coin[1] := a[1];
        real_coin[2] := a[2];
        if real_coin[1] = a[5] then
            forged_coin := 6
        else forged_coin := 5;
    end
    else begin
        real_coin[1] := a[5];
        real_coin[2] := a[6];
        if a[1] + a[2] = real_coin[1] + real_coin[2] then begin
            real_coin[3] := a[1];
            real_coin[4] := a[2];
            if real_coin[1] = a[3] then
                forged_coin := 4
            else forged_coin := 3;
        end

        else begin
            real_coin[3] := a[3];
            real_coin[4] := a[4];
            if real_coin[1] = a[1] then
                forged_coin := 2
            else forged_coin := 1;
        end;
    end;

    writeln(forged_coin);
end.