Loop do not start for letter matching algoritm

[phob0s]

Hello,
I make a simple algoritm to compare two strings, but the loop do not continue to the end. This end is the minimum string lenght from these two data entry.

Here's my code :

j1 = "BB"
j2 = "AABBCCDDEEFFGGHHIIJJKKLLMMBBDCCDEEFFGGHHIIJJKKLLMM"

t = 0
tab = []

if len(j1) < len(j2):
    n = len(j1)
else:
    n = len(j2)

for i in range(n):

    while j1[i] == j2[i]:
        t += 1
        tab.append(t)

print(tab)
print(t)

I have this :

[]
0

I must have this type of result:

[1, 2]
2

For AA in the first string = AA to the second string and the loop stop.

Thanks for any help.