How to create the correct format of JSON?

[luigitofano]

{
    "root": {
        "A": [
            [
                [
                    [
                        1.0000008344650269,
                        -9.0,
                        8.742284762774943e-08
                    ],
                    [
                        4.0,
                        -1.9999996423721313,
                        3.4969113471561286e-07
                    ],
                    [
                        8.999999046325684,
                        12.000000953674316,
                        7.868048896852997e-07
                    ],
                    [
                        14.0,
                        -1.9999988079071045,
                        1.2239188436069526e-06
                    ],
                    [
                        17.0,
                        -8.999998092651367,
                        1.486187329646782e-06
                    ]
                ]
            ],
            [
                [
                    [
                        4.0,
                        -1.9999996423721313,
                        3.4969113471561286e-07
                    ],
                    [
                        14.0,
                        -1.9999988079071045,
                        1.2239188436069526e-06
                    ],
                    [
                        14.0,
                        -1.9999988079071045,
                        1.2239188436069526e-06
                    ],
                    [
                        4.0,
                        -1.9999996423721313,
                        3.4969113471561286e-07
                    ]
                ]
            ]
        ]
    }
}

HersheyText::CharacterDataSet HersheyText::loadCharacterDataSet() {
    CharacterDataSet dataSet;

    // Check if root is an object
    if (!root.isObject()) {
        std::cerr << "Error: 'root' value is not an object." << std::endl;
        return dataSet;
    }

    for (const auto& characterKey : root.getMemberNames()) {
        CharacterData characterData;
        characterData.character = characterKey;

        const Json::Value& characterJson = root[characterKey];
        if (characterJson.isArray()) {
            const Json::Value& characterJson = root[characterKey];
            if (!characterJson.isArray()) { //<-- Unhandled exception
                std::cerr << "Warning: Data for character '" << characterKey << "' is not an array." << std::endl;
                continue;
            }
            parsePolyline(characterJson, characterData.polylines);

        }

        dataSet.characters.push_back(characterData);
    }

    return dataSet;
}

So far the format of this JSON leads to an unhandled exception somewhere on or near the line marked with '<--'... How to solve this? What should the JSON format look like?