import sys
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 = table[i]
    for j in G[i]:
        if table[j] < x:
            table[j] = x
ans = N * (N + 1) // 2 - sum(nodes) + sum(table)
print(ans)