Getting "IndexError" while calculating time intervals

Details:

• There are two cities, a, b. and two arrays representing flight departure time.

• Flight from a to b is represented using array a2b, and flight from b to a is represented using array b2a.

• Flight from a to b and b to a both take 100 minutes.

• Need to take "n" roundtrips between the two cities(a -> b and b -> a is ONE round trip).

• Assume you always take the first flight from a to b and then take the earliest available flights.

Question: Return the time you arrive back at city a.

Example:

a2b = [109, 500]
b2a = [210, 600]
n = 2(roundtrips we need to take)

Explanation:

• Take 109 from a to b, arrive at b at 109 + 100 = 209
• Take 210 from b to a, arrive at 210 + 100 = 310.
• Take 500 from a to b again.
• Arrive at b at 500 + 100 = 600, then take 600 flight back
• Arrive at a at 600 +100 = 700.

My Code:

def flight_time(a2b, b2a, n):
    
    a2b.sort()
    b2a.sort()
    
    trips = 0
    a_arrival_time = 0
    
    i = j = 0
    while trips <= n:
        b_arrival_time = a2b[i] + 100
        i += 1
        
        while j < len(b2a):
            if (b2a[j] - b_arrival_time) < 0:
                j += 1
                continue
            else:
                a_arrival_time = b2a[j] + 100
                j += 1
                trips += 1
                break
      
    return a_arrival_time      

flight_time(a2b, b2a, n)
            

Error IndexError: list index out of range

I also get this error when n becomes large such as n=6.

It looks like the code is not handling all the edge cases.