#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const int borne = 201*1000;
int nbNodes, nbEdges;

vector<int> adj[borne];
bool vu[borne];
vector<pair<int, int>> ivComp;

void dfs(int nod, int& weaker, int& bigger)
{
    vu[nod] = true;
    weaker = min(weaker, nod);
    bigger = max(bigger, nod);

    for (int neighbor : adj[nod]) if (! vu[neighbor]) {
        dfs(neighbor, weaker, bigger);
    }
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> nbNodes >> nbEdges;
    for (int iEdge = 0; iEdge < nbEdges; ++iEdge) {
        int u, v;
        cin >> u >> v;
        --u; --v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    for (int nod = 0; nod < nbNodes; ++nod) {
        if (! vu[nod]) {
            int weaker = nod, bigger = nod;
            dfs(nod, weaker, bigger);
            ivComp.emplace_back(weaker, bigger);
        }
    }

    //sort(ivComp.begin(), ivComp.end()); // Useless, already sorted

    int curEnd = -1;
    int rep = 0;

    for (auto comp : ivComp) {
        if (comp.first <= curEnd) {
            ++rep;
        }
        curEnd = max(curEnd, comp.second);
    }

    cout << rep << "\n";
    return 0;
}