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+#!/usr/bin/env python3
+
+# TASK #1 > Integer Square Root
+# Submitted by: Mohammad S Anwar
+# You are given a positive integer $N.
+# 
+# Write a script to calculate the integer square root of the given number.
+# 
+# Please avoid using built-in function. Find out more about it here.
+# 
+# Examples
+# Input: $N = 10
+# Output: 3
+# 
+# Input: $N = 27
+# Output: 5
+# 
+# Input: $N = 85
+# Output: 9
+# 
+# Input: $N = 101
+# Output: 10
+
+# solution: https://en.wikipedia.org/wiki/Integer_square_root
+
+import sys
+
+def isqrt(n):
+    x0 = n >> 1         # initial estimate
+    if x0 == 0:
+        return n
+    
+    # loop
+    x1 = int(x0 + n/x0) >> 1
+    while x1 < x0:
+        x0 = x1;
+        x1 = int(x0 + n/x0) >> 1
+
+    return x0
+
+n = int(sys.argv[1])
+print(isqrt(n))