import sys # sys.setrecursionlimit(200005) int1 = lambda x: int(x)-1 p2D = lambda x: print(*x, sep="\n") def II(): return int(sys.stdin.readline()) def LI(): return list(map(int, sys.stdin.readline().split())) def LI1(): return list(map(int1, sys.stdin.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def SI(): return sys.stdin.readline().rstrip() dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] # dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] inf = 10**20 md = 998244353 # md = 10**9+7 n,q=LI() ans=0 aa=[0]*n for _ in range(q): l,r=LI() for i in range(l-1,r): if aa[i]: aa[i]=0 ans-=1 else: aa[i]=1 ans+=1 print(ans)