下面C++代码能求整数N和M之间所有整数之和，包含N和M。（    ）

int N, M, Sum;

cin >> N >> M;

if (N > M){

      int tmp = N;

      N = M, M = tmp;

}

for (int i = N; i < M+1; i++)

      Sum += i;

cout << Sum;