function solve (char1, char2) {
    let charCode1 = char1.charCodeAt(0);
    let charCode2 = char2.charCodeAt(0);
    let result = [];

    if (charCode1 > charCode2) {
        [charCode1, charCode2] = [charCode2, charCode1];
    }

    for (let i = charCode1 + 1; i < charCode2; i++) {
        result.push(String.fromCharCode(i));
    }

    return result.join(' ');
}

console.log(solve('C', '#'))