05. Rosetta Stone

function rosettaStone(input) {
    let templateLen = Number(input[0]);
    let template = input.slice(1, templateLen + 1).map((x) => x.split(" ").map(Number));
    let message = input.slice(templateLen + 1).map((x) => x.split(" ").map(Number));
    let encoder = (n) => " ABCDEFGHIJKLMNOPQRSTUVWXYZ"[(n % 27)];

    for (let row = 0; row < message.length; row++) {
        let tRow = template.shift();
        for (let col = 0; col < message[row].length; col += tRow.length) {
            for (let tCol = 0; tCol < tRow.length && col + tCol < message[row].length; tCol++) {
                message[row][col + tCol] += tRow[tCol];
            }
        }
        template.push(tRow);
    }

    let encodingMessage = message.flat().map(x => encoder(x)).join("").trimEnd();
    console.log(encodingMessage);
}