/**
 * @param {number} m
 * @param {number} n
 * @return {number}
 */
var uniquePaths = function (m, n) {
    const f = Array(n).fill(1);
    for (let i = 1; i < m; ++i) {
        for (let j = 1; j < n; ++j) {
            f[j] += f[j - 1];
        }
    }
    return f[n - 1];
};