diff --git a/selftest/misc.py b/selftest/misc.py
new file mode 100755
index 0000000..e57a48c
--- /dev/null
+++ b/selftest/misc.py
@@ -0,0 +1,7 @@
+#!/usr/bin/env python3
+
+msisdn = '0000'
+
+l = len(msisdn)
+next_msisdn = ('%%0%dd' % l) % (int(msisdn) + 1)
+print(next_msisdn)