const readline = require('readline');
 
// Create input interface
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});
 
// Store all input lines
const inputLines = [];
 
// Greet user and give instructions
console.log('Welcome! Please enter lines of text (one per line).');
console.log('When done, press Ctrl+D (Linux/macOS) or Ctrl+C (Windows) or Ctrl+Z then Enter (Windows).');
 
// Store each line
rl.on('line', (line) => {
    inputLines.push(line.trim());
});
 
// When input ends, process and show output
rl.on('close', () => {
    const output = [];
 
    for (const line of inputLines) {
        const freq = {};
 
        for (const char of line) {
            if (char !== ' ') {
                freq[char] = (freq[char] || 0) + 1;
            }
        }
 
        const hasExactlyTwo = Object.values(freq).some(count => count === 2);
 
        if (hasExactlyTwo) {
            output.push(line);
        }
    }
 
    console.log('\nOutput:');
    console.log(output.join('\n'));
});

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