function hasCharacterAppearingExactlyTwice(line) {
    const charCount = {};
 
    for (let char of line) {
        charCount[char] = (charCount[char] || 0) + 1;
    }
 
    return Object.values(charCount).includes(2);
}
 
try {
    while (true) {
        const line = readline();
 
        if (line === null || line === undefined || line === '') {
            break;
        }
 
        if (hasCharacterAppearingExactlyTwice(line)) {
            console.log(line);
        }
    }
} catch (e) {
    console.error("Error: Could not read input. Ensure the environment supports readline().");
}

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