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+#!/usr/bin/env python3
+
+# Challenge 155
+#
+# TASK #2 > Pisano Period
+# Submitted by: Mohammad S Anwar
+# Write a script to find the period of the 3rd Pisano Period.
+#
+# In number theory, the nth Pisano period, written as p(n), is the period with
+# which the sequence of Fibonacci numbers taken modulo n repeats.
+#
+# The Fibonacci numbers are the numbers in the integer sequence:
+#
+# 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, ...
+# For any integer n, the sequence of Fibonacci numbers F(i) taken modulo n is
+# periodic. The Pisano period, denoted p(n), is the value of the period of this
+# sequence. For example, the sequence of Fibonacci numbers modulo 3 begins:
+#
+# 0, 1, 1, 2, 0, 2, 2, 1,
+# 0, 1, 1, 2, 0, 2, 2, 1,
+# 0, 1, 1, 2, 0, 2, 2, 1, ...
+# This sequence has period 8, so p(3) = 8.
+
+from math import isqrt
+
+order = 3
+
+def fibonacci_series(n):
+    fibs = [0, 1]
+    for i in range(2, n):
+        fibs.append(fibs[-1] + fibs[-2])
+    return fibs
+
+def is_period(period, n):
+    base = n[0:period]
+    ord1 = n[period:2*period]
+    ord2 = n[2*period:3*period]
+
+    if base != ord1:
+        return 0
+    if base != ord2:
+        return 0
+    return 1
+
+def find_period(n):
+    period = 1
+    while True:
+        if 3 * period > len(n):
+            return 0
+        if is_period(period, n):
+            return period
+        period += 1
+    return 0
+
+fibs = fibonacci_series(100)
+fibs_mod = [fib % order for fib in fibs]
+print(find_period(fibs_mod))