//fpc 3.0.0

program HelloWorld;
var
    n: Integer;
    head: Array [1..6] of Integer;
    i: Integer;
    j: Integer;
    minEvenNumber: Integer;
    minOddNumber: Integer;
    inputNumber: Integer;
    first: Integer;
    minResult: Longint;
    currentResult: Longint;
    solutionExists: Boolean;
begin
    minEvenNumber := 10001;
    minOddNumber := 10001;
    minResult := 10000000000;
    solutionExists := false;
    readln(n);
    for i:=1 to n do
    begin
        readln(inputNumber);
        if i <= 6 then
        begin
            head[i] := inputNumber;
        end
        else
        begin
            first := head[1];
            for j:=1 to 5 do
                head[j] := head[j+1];
            head[6] := inputNumber;
            if (first < minEvenNumber) and (first mod 2 = 0) then
                minEvenNumber := first;
            if (first < minOddNumber) and (first mod 2 = 1) then
                minOddNumber := first;

            if (inputNumber mod 2 = 0) then
            begin
                solutionExists := true;
                currentResult := minEvenNumber * inputNumber;
                if (currentResult < minResult) then
                    minResult := currentResult;

                currentResult := minOddNumber * inputNumber;
                if (currentResult < minResult) then
                    minResult := currentResult;
            end
            else
            begin
                currentResult := minEvenNumber * inputNumber;
                if (currentResult < minResult) then
                    minResult := currentResult;
            end;
        end
    end;
    if solutionExists then
        writeln(minResult)
    else
        writeln(-1);

end.