import sys
from collections import deque
input = sys.stdin.buffer.readline

N, M = map(int, input().split())
BC = [tuple(map(int, input().split())) for _ in range(M)]

nodes = set()
for b, c in BC:
    nodes.add(b)
    nodes.add(c)
nodes = sorted(nodes)
comp = {x: i for i, x in enumerate(nodes)}
L = len(comp)

G = [[] for _ in range(L)]
for b, c in BC:
    G[comp[c]].append(comp[b])

table = nodes.copy()
for i in range(L - 1, -1, -1):
    x = nodes[i]
    if x < table[i]:
        continue
    d = deque([i])
    while d:
        v = d.pop()
        for u in G[v]:
            if table[u] < x:
                table[u] = x
                d.append(u)
ans = N * (N + 1) // 2 - sum(nodes) + sum(table)
print(ans)