<doocs>1426.Counting Elements_1.py
def countElements( arr: List[int]) -> int:
    s = set(arr)
    return sum(x + 1 in s for x in arr)
def sample_funcname ( var_0 : List [ int ] ) -> int :
    var_4 = set ( var_0 )
    return sum ( var_6 + 1 in var_4 for var_6 in var_0 )
