t=input().split() m=int(t[0]) n=int(t[1]) a=input().split() a1=int(a[0]) a2=int(a[1]) b=input().split() b1=int(b[0]) b2=int(b[1]) c=input().split() c1=int(c[0]) c2=int(c[1])

k=set() for i in range(a1,a2+1): k.add(i) for i in range(b1,b2+1): k.add(i) for i in range(c1,c2+1): k.add(i) sum=m-0+1 print(sum-len(k))