Flatten Nested Dictionary

Given a nested dictionary represented in JSON format, your task is to flatten the dictionary so that the keys of nested dictionaries are concatenated into a single key using an underscore as a separator. The flattening should be performed recursively for arbitrarily deep nesting.

For example, the nested dictionary \[ {"a": 1, "b": {"c": 2, "d": 3}} \] should be flattened to \[ {"a": 1, "b_c": 2, "b_d": 3} \] Note that if further nesting occurs, like \[ {"a":1, "b": {"c": {"d": {"e": 2}}}, "f": {"g":3}} \] then the flattened output would be \[ {"a": 1, "b_c_d_e": 2, "f_g": 3} \] Input is provided in JSON format via stdin and the result should be printed to stdout as a JSON object.

inputFormat

The input consists of a single line containing a valid JSON object that represents a nested dictionary. Each key is a string and each value is either an integer or another JSON object. You can assume that the input is well-formed.

outputFormat

Output a single JSON object representing the flattened dictionary where nested keys are concatenated using an underscore ('_') as separator.

{"a": 1, "b": 2}

{"a":1,"b":2}