fenwick-add-range

inline void add(int ind, int val)
{
	for (; ind <= n + 1; ind += ind & -ind)
		fen[ind] += val;
}

inline void range_add(int l, int r, int val)
{
	add(l, val);
	add(r + 1, -val);
}

inline int get_val(int ind)
{
	int ret = 0;
	for (; ind; ind -= ind & -ind)
		ret += fen[ind];
	return ret;
}