int maxlen(vector<int> v)
{
    int hi = n, lo = 1, ans = -1, mid, cnt = 0;
    while(lo <= hi) {
        mid = hi+lo>>1;
        if(cnt = count(mid)) {
            ans = mid;
            lo = mid + 1;
        } else {
            hi = mid - 1;
        }
 }

int count(int len) {
    int cnt = 0;
    for(int i = len; i <= n; i++)
        if(prefixsum[i] - prefixsum[i - len] > K)
            cnt++;
    return cnt;
}