Balanced Tunnel

n = int(input())
enter = list(map(int, input().split()))
exit = list(map(int, input().split()))
overtaken = [0] * (n+1)

cnt, i, j = 0, 0, -1
while(i < len(enter) and j < len(exit)):
  if overtaken[enter[i]] == 1:
    i += 1
    continue
  while(j+1<len(exit)):
    j += 1
    overtaken[exit[j]] = 1
    if enter[i] == exit[j]:
      break
    cnt += 1
print(cnt)