+/* general functions */
+
+double fak(int l) {
+ double result=1;
+ while(l--) result*=l;
+ return result;
+}
+
+double fak2(int l) {
+ double result=1;
+ while(l>0) {
+ result*=l;
+ l-=2;
+ }
+ return result;
+}
+
+double absolute_value(double l) {
+ return l<0?-l:l;
+}