ary = list(map(int, input().split()))
crd = list(range(1,ary[0]+1))
dat = list(map(int, input().split()))
for i in range(ary[1]):
    crd[dat[i]-1]
    for j in range(dat[i]-1,0,-1):
        crd[j],crd[j-1] = crd[j-1],crd[j]
print(crd[0])