class Solution {
public:
    int longestWPI(vector<int>& hours) {
        int len = hours.size();
        vector<int> sum(len+1);
        sum[0] = 0;
        for (int i = 0; i < len; i++) {
            hours[i] = hours[i] > 8 ? 1 : -1;
            sum[i+1] = sum[i] + hours[i];
        }
        for (int i = len; i > 0; i--) {
            for (int j = 0, k = j + i; k <= len; j++, k++) {
                if (sum[k] - sum[j] > 0) return i;
            }
        }
        return 0;
    }
};