import itertools as iter import collections as coll import heapq as hq import bisect as bis from decimal import Decimal as dec from functools import cmp_to_key import math import sys #import pypyjit #pypyjit.set_param('max_unroll_recursion=-1') sys.setrecursionlimit(10 ** 6) inp = sys.stdin.readline input = lambda : inp().rstrip() getN = lambda : int(inp()) getNs = lambda : map(int, inp().split()) getList = lambda :list(map(int, inp().split())) getStrs = lambda n : [input() for _ in [0] * n] def yexit(): print("Yes"); exit(0) def nexit(): print("No"); exit(0) pi = 3.141592653589793 mod = 1000000007 MOD = 998244353 INF = 4611686018427387903 dx = [1, 0, -1, 0]; dy = [0, 1, 0, -1] #di = coll.defaultdict(int) """ Main Code """ n, m = getNs() imos = [0] * (n + 1) for l, r in [getList() for _ in [0]*m]: imos[n - l] += 1 imos[n - r + 1] -= 1 now = 0 for k in imos[:n]: now += k print(now)