#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(abs(a), abs(b));}
ll lcm(ll a, ll b){return abs(a) / gcd(a, b) * abs(b);}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ull mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
struct DSU{
int n;
vector<int> parent, sz;
DSU(int _n){
n = _n;
parent.resize(n); sz.resize(n, 1);
for(int i = 0; i<n; ++i) parent[i] = i;
}
int find_set(int u){return (u == parent[u]) ? u : (parent[u] = find_set(parent[u]));}
bool same_set(int u, int v){return find_set(u) == find_set(v);}
bool join_set(int u, int v){
u = find_set(u), v = find_set(v);
if (u != v){
if (sz[u] < sz[v]) swap(u, v);
parent[v] = u;
sz[u] += sz[v];
return true;
}
return false;
}
int get_size(int u){return sz[find_set(u)];}
};
const int N = 2e6 + 69;
int graph[N];
void solve(){
int n, m; cin >> n >> m;
vector<pair<int, int>> a(n);
for(int i = 0; i < n; ++i) cin >> a[i].first >> a[i].second;
vector<int> X;
for(auto i: a){
X.push_back(i.first);
X.push_back(i.second);
}
X.push_back(0);
remove_dup(X);
for(auto i: a){
int l = lower_bound(ALL(X), i.first) - X.begin() - 1;
int r = lower_bound(ALL(X), i.second) - X.begin();
graph[l] = r;
graph[r-1] = l+1;
}
int t = X.size();
DSU mst(t);
for(int i = 0; i < t; ++i){
mst.join_set(i, graph[i]);
}
int ans = mst.get_size(0) - 1;
vector<int> cc;
for(int i = 0; i < t; ++i) if (!mst.same_set(0, i) && mst.find_set(i) == i){
cc.push_back(mst.get_size(i));
}
sort(ALL(cc));
if (cc.empty()) assert(false);
if (m > 1 && cc.empty()){
cc.push_back(1);
m--;
ans++;
}
while(m--){
if (cc.size()){
int u = cc.back(); cc.pop_back();
ans += u + 2;
}
else{
ans += 2;
}
}
cout << ans << "\n";
}
int main(void){
ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << "ms!\n";
return 0;
}
