N,D = map(int,raw_input().split())
x = [0] * N
sw = 0
z1 = 0
z2 = 0
count = 0

#演算
while sw == 0:
     x[z2] = 1
     z2 = (z2 + D) % N
    
#移動先の判定
     if x[z2] != 1:
          count += 1
     else:
          sw = 1

print count