#include <bits/stdc++.h>
using namespace std;
using vi = vector<long long int>;
using vvi = vector<vi>;
using vb = vector<bool>;
using vc = vector<char>;
using vs = vector<string>;
using vld = vector<long double>;
using pii = pair<long long int, long long int>;
using psi = pair<string, long long int>;
using pci = pair<char, long long int>;
using vpii = vector<pii>;
long long int mod = 1e9 + 7;
long long int const maxn = 2e5 + 5;
long long int const inf = 1e18;
long long int add(long long int a, long long int b) {
  return ((a % mod) + (b % mod)) % mod;
}
long long int mul(long long int a, long long int b) {
  return ((a % mod) * (b % mod)) % mod;
}
long long int powm(long long int x, long long int n, long long int M) {
  long long int result = 1;
  while (n > 0) {
    if (n % 2 == 1) result = (result * x) % M;
    x = (x * x) % M;
    n = n / 2;
  }
  return result;
}
long long int modinverse(long long int a, long long int m) {
  return powm(a, m - 2, m);
}
bool prime(long long int x) {
  if (x <= 1) return false;
  for (int i = 2; i <= sqrt(x); i++)
    if (x % i == 0) return false;
  return true;
}
long long int divisor(long long int x) {
  long long int cnt = 0;
  for (int i = 1; i <= sqrt(x); i++) {
    if (x % i == 0) {
      if (i != x / i)
        cnt += 2;
      else
        cnt += 1;
    }
  }
  return cnt;
}
vector<long long int> sieve(long long int n) {
  bool prim[n + 1];
  memset(prim, true, sizeof(prim));
  for (long long int p = 2; p * p <= n; p++) {
    if (prim[p] == true) {
      for (int i = p * p; i <= n; i += p) prim[i] = false;
    }
  }
  vector<long long int> v;
  for (int i = 2; i <= n; i++)
    if (prim[i]) v.push_back(i);
  return v;
}
vvi adj(maxn);
vb vis(maxn, false);
long long int x, y;
void dfs(long long int u) {
  if (vis[u] == true) return;
  vis[u] = true;
  if (x == -1 and y == -1) {
    x = u;
    y = u;
  }
  x = min(x, u);
  y = max(y, u);
  for (auto v : adj[u]) {
    if (!vis[v]) {
      dfs(v);
    }
  }
}
int main() {
  int t;
  t = 1;
  while (t--) {
    long long int n, m;
    cin >> n >> m;
    vpii ans;
    for (long long int i = 0; i < m; i++) {
      long long int a, b;
      cin >> a >> b;
      adj[a].push_back(b);
      adj[b].push_back(a);
    }
    for (long long int i = 1; i <= n; i++) {
      if (!vis[i]) {
        x = -1;
        y = -1;
        dfs(i);
        ans.push_back({x, y});
      }
    }
    sort(ans.begin(), ans.end());
    long long int cnt = 0;
    for (long long int i = 1; i <= (long long int)ans.size() - 1; i++) {
      if (ans[i - 1].second >= ans[i].first) {
        cnt++;
        ans[i].second = max(ans[i - 1].second, ans[i].second);
      }
    }
    cout << cnt << "\n";
  }
  return 0;
}
