#coding: utf-8
nNums=list(map(int,input().split()))

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


print(nAns)