(format LCTRS :logic QF_LIA)
(fun return 1 :sort (Int Int))
(fun sum1 1 :sort (Int Int))
(fun u 3 :sort (Int Int Int Int))

(rule (sum1 n) (u n 1 0) :vars ((n Int)))
(rule (u n i k) (u n (+ i 1) (+ k i)) :guard (<= i n) :vars ((n Int) (i Int) (k Int)))
(rule (u n i k) (return k) :guard (not (<= i n)) :vars ((n Int) (i Int) (k Int)))