refactor various files

S1/GdCP/uebung/square.c

@@ -0,0 +1,14 @@
+#include <stdio.h>
+
+int main() {
+    int num, sum = 0;
+    scanf("%d", &num);
+
+    while (num > 0) {
+        sum += num % 10;
+        num /= 10;
+    }
+
+    printf("%d\n", sum);
+    return 0;
+}