title: Find Repetitive Element 1 N 1
signature: findRepetitiveElement1N1 :: [Integer] -> Integer -> Integer
  findRepetitiveElement1N1 arr n = 
test_code: import Text.Printf
  import Control.Exception (catch, SomeException)
  import Data.Typeable
  import qualified Data.List as List
  import qualified Data.Map as Map
  import qualified Data.Set as Set
  
  -- SOLUTION CODE
  -- ============================================
  
  PLACEHOLDER_CODE_BODY
  
  -- TESTING CODE 
  -- ============================================
  validateSolution :: Integer -> Integer -> Bool
  validateSolution actual expected = do
      actual == expected
  
  
  driver :: [Integer] -> Integer -> Integer -> String
  driver arr n expected = do
      if (validateSolution (PLACEHOLDER_FN_NAME arr n) expected)
          then "PASSED"
      else "FAILED"
  
  main = do
      printf "TEST-0...%s\n" (driver ([4, 8, 27, 34, 39, 42, 43, 54, 72]) (5) (313) )
  
      printf "TEST-1...%s\n" (driver ([-38, -66, -38, -48, -96, 74, -32, -62, -34, -32, -88, -12, -8, -4]) (9) (-520) )
  
      printf "TEST-2...%s\n" (driver ([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1]) (8) (-23) )
  
      printf "TEST-3...%s\n" (driver ([88, 86, 23, 81, 76, 16, 94, 64, 59, 50, 71, 62, 10, 89, 73, 64, 65, 96, 83, 40, 99, 40, 77, 33, 14, 62, 6, 89, 74, 96, 93, 29, 15, 93, 9, 58, 98, 76, 23, 23, 70, 99]) (31) (2101) )
  
      printf "TEST-4...%s\n" (driver ([-96, -94, -82, -64, -56, -40, -36, -34, -32, -24, -24, -22, -20, -20, -20, -18, -18, -12, -10, -6, 16, 20, 20, 22, 26, 30, 36, 46, 46, 50, 50, 52, 64, 64, 64, 68, 72, 74, 76, 92, 96, 98]) (28) (76) )
  
      printf "TEST-5...%s\n" (driver ([0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1]) (25) (-288) )
  
      printf "TEST-6...%s\n" (driver ([2, 6, 7, 13, 19, 23, 37, 39, 42, 42, 43, 45, 52, 53, 55, 56, 59, 63, 66, 71, 76, 85, 86, 89, 92, 94, 96, 99]) (27) (1159) )
  
      printf "TEST-7...%s\n" (driver ([52, -56, -12, 78, 6, 32, 0, 36, 34, -54, -74, -32]) (11) (-45) )
  
      printf "TEST-8...%s\n" (driver ([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]) (15) (-86) )
  
      printf "TEST-9...%s\n" (driver ([10, 42, 50, 5, 74, 81, 30, 76, 6, 34, 86, 4, 77, 71, 96, 22, 34, 50, 35, 16, 60, 11, 21, 38]) (13) (951) )
  
source_py: def find_repetitive_element_1_n_1(arr, n):
      return (sum(arr) - (((n - 1) * n) // 2))
source_cpp: int find_repetitive_element_1_n_1(vector<int> arr, int n) {
    return accumulate(arr.begin(), arr.end(), 0 ) - ( ( n - 1 ) * n / 2 );
  }