function countingValleys(n, s) {
    let result = 0;
    const arr = s.split("")
                 .map(v => (v === 'U') ? 1 : -1)
                 .reduce((a, c) => {
                    if (a + c === 0 && a < 0) result += 1;
                    return a + c;
                 }, 0);
    return result;
}