diff --git a/hydrogentest.py b/hydrogentest.py
new file mode 100644
index 0000000..42c5947
--- /dev/null
+++ b/hydrogentest.py
@@ -0,0 +1,18 @@
+#!/bin/python3
+a="ksabvdkbvksajbvkjsabvkjsabvkjabsvkjsabvbvghahfksajfkjhcxvsLHREFIsdfsdfsdfasdfasdfasfd"
+b="kucasdhkausughaksdflsad iajfdaslfdlgajldsag asldivclsadgnaksndglkasdjasdvc"
+def longest_common_substring(s1, s2):
+   m = [[0] * (1 + len(s2)) for i in range(1 + len(s1))]
+   longest, x_longest = 0, 0
+   for x in range(1, 1 + len(s1)):
+       for y in range(1, 1 + len(s2)):
+           if s1[x - 1] == s2[y - 1]:
+               m[x][y] = m[x - 1][y - 1] + 1
+               if m[x][y] > longest:
+                   longest = m[x][y]
+                   x_longest = x
+           else:
+               m[x][y] = 0
+   return s1[x_longest - longest: x_longest]
+
+print(longest_common_substring(a, b))