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+#+title: Challenge 133
+#+date: 2021-10-04
+#+html_link_up: ../
+#+export_file_name: index
+#+options: toc:nil
+#+setupfile: ~/.emacs.d/org-templates/level-2.org
+
+* Task 1 - Integer Square Root
+
+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 [[https://en.wikipedia.org/wiki/Integer_square_root][here]].
+
+#+begin_src
+Input: $N = 10
+Output: 3
+
+Input: $N = 27
+Output: 5
+
+Input: $N = 85
+Output: 9
+
+Input: $N = 101
+Output: 10
+#+end_src
+
+** Raku
+
+- Program: [[file:raku/ch-1.raku]]
+
+Initial estimate is set to ~$n +> 1~, then we loop infinitely until
+previous 2 estimates are equal.
+
+#+begin_src raku
+my $x = $n +> 1;
+loop {
+    given ($x + ($n / $x)) / 2 {
+        last if $x == $_;
+        $x = $_;
+    }
+}
+put $x;
+#+end_src
+
+** C
+
+- Program: [[file:c/ch-1.c]]
+
+~argv~ holds the input & ~argc~ holds the number of inputs. The input should
+be a single integer so ~argc~ should be equal to 2. After checking for
+that, we check if valid value was passed.
+
+Loop until previous 2 estimates are equal.
+
+#+begin_src c
+double x = num >> 1;
+for (;;) {
+    double x_next = (x + (num / x)) / 2;
+    if (x == x_next)
+        break;
+    x = x_next;
+ }
+printf("%f\n", x);
+#+end_src