Hi, @Reshma,

You can go through this as an example:

def count(a, b, m, n):
# If both first and second string
# is empty, or if second string
# is empty, return 1
if ((m == 0 and n == 0) or n == 0):
return 1
# If only first string is empty
# and second string is not empty,
# return 0
if (m == 0):
return 0
# If last characters are same
# Recur for remaining strings by
# 1. considering last characters
# of both strings
# 2. ignoring last character
# of first string
if (a[m - 1] == b[n - 1]):
return (count(a, b, m - 1, n - 1) +
count(a, b, m - 1, n))
else:
return count(a, b, m - 1, n)
print(count(a, b, len(a),len(b)))

**Output:**

4