import sys from collections import defaultdict, Counter, deque from itertools import permutations, combinations, product, combinations_with_replacement, groupby, accumulate import operator from math import sqrt, gcd, factorial #from math import isqrt, prod, comb #python3.8用(notpypy) #from bisect import bisect_left, bisect_right #from functools import lru_cache, reduce #from heapq import heappush, heappop, heapify, heappushpop, heapreplace #import numpy as np #import networkx as nx #from networkx.utils import UnionFind #from numba import njit, b1, i1, i4, i8, f8 #numba例 @njit(i1(i4[:], i8[:, :]),cache=True) 引数i4配列、i8 2次元配列,戻り値i1 #from scipy.sparse import csr_matrix #from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson, NegativeCycleError, maximum_bipartite_matching, maximum_flow, minimum_spanning_tree def input(): return sys.stdin.readline().rstrip() def divceil(n, k): return 1+(n-1)//k # n/kの切り上げを返す def yn(hantei, yes='Yes', no='No'): print(yes if hantei else no) def main(): mod = 10**9+7 mod2 = 998244353 n,q=map(int, input().split()) ans=0 check=[0]*(n+5) for j in range(q): l,r=map(int, input().split()) for i in range(l,r+1): if check[i]==0: check[i]=1 ans+=1 else: check[i]=0 ans-=1 print(ans) if __name__ == '__main__': main()