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diff --git a/challenge-099/paulo-custodio/python/ch-2.py b/challenge-099/paulo-custodio/python/ch-2.py
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+#!/usr/bin/env python
+
+# Challenge 099
+# 
+# TASK #2 > Unique Sub-sequence
+# Submitted by : Mohammad S Anwar
+# You are given two strings $S and $T.
+#
+# Write a script to find out count of different unique sub-sequences matching
+# $T without changing the position of characters.
+#
+# Example 1:
+# Input : $S = "littleit', $T = 'lit'
+# Output : 5
+#
+#     1: [lit] tleit
+#     2: [li] t[t] leit
+#     3: [li] ttlei[t]
+#     4: litt[l] e[it]
+#     5: [l] ittle[it]
+# Example 2:
+# Input : $S = "london', $T = 'lon'
+# Output : 3
+#
+#     1: [lon] don
+#     2: [lo] ndo[n]
+#     3: [l] ond[on]
+
+import sys
+
+def count_subsequences(s, t):
+    while True:
+        if t=="":
+            return 1
+        elif s=="":
+            return 0
+        elif s[0]==t[0]:
+            return (count_subsequences(s[1:], t[1:]) +
+                    count_subsequences(s[1:], t))
+        else:
+            s=s[1:]
+
+print(count_subsequences(sys.argv[1], sys.argv[2]))