title: Find Repetitive Element 1 N 1
signature: function find_repetitive_element_1_n_1(arr, n)
test_code: using Printf
  
  # SOLUTION CODE
  # ============================================
  PLACEHOLDER_CODE_BODY
  
  # TESTING CODE 
  # ============================================
  function validate_solution(actual, expected)
      return actual == expected
  end
  
  function driver(arr, n, expected)
      try
  
          if validate_solution(PLACEHOLDER_FN_NAME(arr, n), expected)
              return "PASSED";
          end
          return "FAILED";
      catch exception_obj
          return string(Base.typename(typeof(exception_obj)).wrapper);
      end
  end
  
  function main()
      
      result = driver([4, 8, 27, 34, 39, 42, 43, 54, 72], 5, 313);
      @printf("TEST-0...%s\n",result);
      
      result = driver([-38, -66, -38, -48, -96, 74, -32, -62, -34, -32, -88, -12, -8, -4], 9, -520);
      @printf("TEST-1...%s\n",result);
      
      result = driver([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1], 8, -23);
      @printf("TEST-2...%s\n",result);
      
      result = 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-3...%s\n",result);
      
      result = 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-4...%s\n",result);
      
      result = 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-5...%s\n",result);
      
      result = 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-6...%s\n",result);
      
      result = driver([52, -56, -12, 78, 6, 32, 0, 36, 34, -54, -74, -32], 11, -45);
      @printf("TEST-7...%s\n",result);
      
      result = 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-8...%s\n",result);
      
      result = 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);
      @printf("TEST-9...%s\n",result);
      
  end
  
  main()
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 );
  }