print multInv(42, 2017)
end
sub multInv(a,b)
x0 = 0
b0 = b
multInv = 1
if b = 1 return
while a > 1
q = a / b
t = b
b = mod (a, b)
a = t
t = x0
x0 = multInv - q * x0
multInv = int(t)
wend
if multInv < 0 return multInv + b0
end sub