AoC day 25, Smalltalk

#!/usr/local/bin/gst -q

subject_num := 7.
mod := 20201227.

public := (stdin contents tokenize: '\n') collect: [ :v | v asNumber ].

p1 := public at: 1.
p2 := public at: 2.

loop := 0.
val  := 7.
[(val ~= p1) and: [val ~= p2]] whileTrue: [
    val := (val * subject_num) \\ mod.
    loop := loop + 1.
].

other := public detect: [ :v | v ~= val ].
encrypt_key := other.
loop timesRepeat: [ encrypt_key := (encrypt_key * other) \\ mod ].
encrypt_key displayNl.