int Solution::numRange(vector<int> &A, int B, int C) {
    int ans=0,size = A.size();
    vector<long long> prefixSum(size, 0);
    prefixSum[0] = A[0];
    for(int i = 1; i < size; i++) prefixSum[i]= prefixSum[i-1] + A[i];
    int l = 0, r = 0;
    long long value = 0;
    for(int i=0; i < size; i++) {
        value = (i == 0) ? 0 : prefixSum[i-1];
        while(l < size and prefixSum[l] < (value + 1ll*B)) l++;
        while(r < size and prefixSum[r] <= (value + 1ll*C)) r++;
        ans += r - l;
    }
    return ans;
}