#coding: utf-8
# if ~:
# for ~:

nNums=list(map(int,input().split()))

if nNums[0]<nNums[1] :
    nAns=(nNums[1]-nNums[0])-1
    nAns=nAns+(nNums[0]-1)
else :
    nAns=(2000000000-nNums[0])+(nNums[0]-nNums[1]-1)


print(nAns)