Why my code is showing tle error

[rahul-kumar_693_602]

    A = nums
    n = len(A)
    i = 0
    while i<n:
      cp = A[i] -1
      if 1 <= A[i] <= n:
          if A[i] != A[cp]:
              A[i], A[cp] = A[cp], A[i]
              i = i - 1
      i = i+1   
      
    for j in range(n):
      if j+1 != A[j]:
         return(j+1)
    return(n+1)

This is my code in python 3. why it is showing TLE