Fuction and sumif problem

hello all I would like some help concerning a function.So i would like to sum some numbers from the collum B based on a criteria.The criteria is that the respective cell in collum A has to have length bigger than 4.So i was thinking because the things inserted in collum A are numbers i could use the >9999 which is the biggest number which has 4 digits but this doesnt work because the numbers are inserted in this format ="7777" and then i guessed i could make this work with the len fuction but i cant make it work in the sumif fuction any help pliz?

thanks in advance

ps here is a sample i made