N,Q=map(int,input().split())
dp=[0]*(N+1)
for _ in range(Q):
    l,r=map(int,input().split())
    dp[l-1]+=1 
    dp[r]+=-1 
ans=0
for i in range(N):
    ans+=dp[i]%2
    dp[i+1]+=dp[i]
print(ans)