Add C solution

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+/*
+Challenge 022
+
+Task #1
+Write a script to print first 10 Sexy Prime Pairs. Sexy primes are prime
+numbers that differ from each other by 6. For example, the numbers 5 and 11
+are both sexy primes, because 11 - 5 = 6. The term "sexy prime" is a pun
+stemming from the Latin word for six: sex. For more information, please
+checkout wiki page.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+bool is_prime(int n) {
+    if (n <= 1)
+        return false;
+    if (n <= 3)
+        return true;
+    if ((n % 2) == 0 || (n % 3) == 0)
+        return false;
+    for (int i = 5; i * i <= n; i += 6)
+        if ((n % i) == 0 || (n % (i + 2)) == 0)
+            return false;
+    return true;
+}
+
+int next_prime(int n) {
+    if (n <= 1)
+        return 2;
+    do {
+        n++;
+    } while (!is_prime(n));
+    return n;
+}
+
+void print_sexy_primes(int count) {
+    int a = 1;
+    while (count > 0) {
+        a = next_prime(a);
+        int b = a;
+        while (b < a+6)
+            b = next_prime(b);
+        if (b == a+6) {
+            printf("(%d, %d)\n", a, b);
+            count--;
+        }
+    }
+}
+
+int main() {
+    print_sexy_primes(10);
+}