Description

现在有N种冰淇淋，TZ要吃他们。
由于TZ食量有限，他等下还要去吃若菜，所以他只吃3个。
然而因为TZ比较神，所以他觉得某两个冰淇淋不能一起吃。
一共有M组不能一起吃的冰淇淋。
TZ可以瞬间算出一共有多少中吃法（[1,2,3]和[2,1,3]是同种）,
你能吗?

n<=200,m<=10000

Input

Output

Sample Input

Sample Output

Hint

There are 5 flavors and 3 impossible pairings. Flavor 1 should be combined with neither flavor 2 nor

flavor 3, and flavor 3 also should not be chosen together with flavor 4. Only 3 ways to choose three

different flavors remain: (1 4 5), (2 3 5), and (2 4 5).

Source