Pseudo Algorithm

It's a basic algorithm that i got half way through.

Write an algorithm that for an entered number from 100 to 10,000 prints if the number has 3, 4 or 5 numbers (Ex. 100, 1000 or 10000)

Algorithm: Proizvod
Start
Read: proizvod, m, n
??? <- 12
proizvod <- 1
While m (Is equal or smaller than) n execute (извршувај)
proizvod (производ) = proizvod + n

What do i do now? Sorry if i didn't translate it well.

@4 I didn't want it to be in C++, just in pseudo.