const fs = require('fs');
const step = 50;

let input = fs.readFileSync('cdf-full.dat', 'utf-8')
    .split('\n')
    .map((x) => x.split(' '));

let output = [];

for (let i = 0; i < input.length; i += step) {
    output.push(input[i]);
}

fs.writeFileSync('cdf.dat', output.map((x) => x.join(' ')).join('\n'));