import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)

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

for b, c in BC:
    val.add(b)
    val.add(c)

val = sorted(val)
vtoi = {v: i for i, v in enumerate(val)}
sz = len(val)
G = [set() for _ in range(sz)]
for b, c in BC:
    b = vtoi[b]
    c = vtoi[c]
    G[c].add(b)

vis = [0] * sz
score = list(range(sz))

for i in reversed(range(sz)):
    if vis[i]:
        continue
    vis[i] = 1
    q = [i]
    while q:
        s = q.pop()
        for t in G[s]:
            if vis[t]:
                continue
            vis[t] = 1
            score[t] = score[s]
            q.append(t)

ans = N * (N + 1) // 2
for i, v in enumerate(score):
    ans -= val[i]
    ans += val[v]
print(ans)