# findFavNum(a,b)は[a,b)の区間について探索する
def findFavNum(a,b)

    if a<b then
        range_left = a
        range_right = b
    else
        range_left = b
        range_right = a
    end
    
    middle = ((range_left-range_right).abs)/2 + range_left
    puts("? #{middle}")
    STDOUT.flush
    if gets.to_i == 1 then
        if (middle-range_right).abs==1 then
            puts("! #{middle}")
            STDOUT.flush
            return
        else 
            findFavNum(middle,range_right)
        end
    else
        if (range_left-middle).abs==1 then
            puts("! #{range_left}")
            STDOUT.flush
            return
        else 
            findFavNum(range_left,middle)
        end
    end
end

findFavNum(1,10**9+1)