const l = s.length;
    const words = Math.ceil(Math.sqrt(l));
    const letters = Math.floor(Math.sqrt(l));
    const d = Number.isInteger(Math.sqrt(l)) ? 0 : 1;
    let r = '';
    
    for(let i =0; i<words; i++) {
        for(let j = i; j < l; j += letters + d) {
            r += s[j];
        }
        r += ' '; // 1 space
    }
    
    return r;