const tower = function(n) {
    let print = [[1, 3]];
    let ans = Math.pow(2, n) - 1;

    for (let i = 2; i <= n; i++) {
        print = swap(2, 3, print).concat([[1, 3]]).concat(swap(1, 2, print));
    }

    console.log(ans);

    for (let i = 0; i < print.length; i++) {
        console.log(print[i].join(" "));
    }
}

const swap = function(i, j, list) {
    let res = copy(list);

    for (let k = 0; k < list.length; k++) {
        for (let l = 0; l < 2; l++) {
            if (list[k][l] == i) {
                res[k][l] = j;
            }
            if (list[k][l] == j) {
                res[k][l] = i;
            }
        }
    }

    return res;
}

const copy = function(list) {
    let res = [];

    for (let i = 0; i < list.length; i++) {
        res.push([]);

        for (let j = 0; j < list[i].length; j++) {
            res[i].push(list[i][j]);
        }
    }

    return res;
}