#ifdef LOCAL
//#define _GLIBCXX_DEBUG
#else
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//#pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#endif

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<char> Vc;
typedef vector<P> VP;
typedef vector<VP> VVP;
typedef vector<Vec> VV;
typedef vector<Vi> VVi;
typedef vector<Vc> VVc;
typedef vector<VV> VVV;
typedef vector<VVV> VVVV;
typedef vector<VVVV> VVVVV;
typedef vector<VVVV> VVVVVV;
#define MAKEVV(variable, a, ...) VV variable(a, Vec(__VA_ARGS__))
#define MAKEVVc(variable, a, ...) VVc variable(a,Vc(__VA_ARGS__))
#define MAKEVVV(variable, a, b, ...) VVV variable(a, VV(b, Vec(__VA_ARGS__)))
#define MAKEVVVV(variable, a, b, c, ...) VVVV variable(a, VVV(b, (VV(c, Vec(__VA_ARGS__)))))
#define MAKEVVVVV(variable, a, b, c, d, ...) VVVVV variable(a, VVVV(b, (VVV(c, VV(d, Vec(__VA_ARGS__))))))
#define MAKEVVVVVV(variable, a, b, c, d, e, ...) VVVVVV variable(a, VVVVV(b, (VVVV(c, VVV(d, VV(e, Vec(__VA_ARGS__)))))))

#define endl '\n'
#define REP(i, a, b) for(ll i=(a); i<(b); i++)
#define PER(i, a, b) for(ll i=(a); i>=(b); i--)
#define rep(i, n) REP(i, 0, n)
#define per(i, n) PER(i, n, 0)
const ll INF = 4'000'000'000'000'000'010LL;
const ll MOD=998244353;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define YES(n) cout << ((n) ? "YES" : "NO") << endl;
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a,b)
#define Each(a,b) for(auto &a :b)
#define rEach(i, mp) for (auto i = mp.rbegin(); i != mp.rend(); ++i)
#define SUM(a) accumulate(ALL(a),0LL)
#define outminusone(a) cout<< ( a==INF ? -1 : a ) <<endl
#define Uniq(v) v.erase(unique(v.begin(), v.end()), v.end())
#define fi first
#define se second

template<class T, class S>bool chmax(T &a, const S &b) { if (a<b) { a=b; return true; } return false; }
template<class T, class S>bool chmin(T &a, const S &b) { if (b<a) { a=b; return true; } return false; }
template<class T>auto lb(vector<T> &X, T x){return lower_bound(ALL(X),x) - X.begin();}
template<class T>auto ub(vector<T> &X, T x){return upper_bound(ALL(X),x) - X.begin();}
ll popcnt(ll x){return __builtin_popcount(x);}
ll topbit(ll t){return t==0?-1:63-__builtin_clzll(t);}
ll floor(ll y,ll x){assert(x != 0);if(x < 0){y *= -1; x *= -1;}if(y < 0){return (y-x+1)/x;}return y/x;};
ll ceil(ll y, ll x){assert(x != 0);if(x < 0){y *= -1; x *= -1;}if(y < 0){return y/x;}return (y+x-1)/x;};

template<typename T1, typename T2>istream &operator>>(istream &i, pair<T1, T2> &p) { return i>>p.first>>p.second; }
template<typename T>istream& operator>>(istream&i,vector<T>&v){rep(j,v.size())i>>v[j];return i;}
template<typename T1, typename T2>ostream &operator<<(ostream &s, const pair<T1, T2> &p) { return s<<"("<<p.first<<", "<<p.second<<")"; }
template<class T>ostream &operator<<(ostream &os, const vector<T> &v) {bool f = false;for(const auto &d: v) {if(f) os<<" ";f = true;os<<d;}return os;}
template <class T> ostream& operator<<(ostream& os, const set<T>& s) {os << "{";bool f = false;for (auto d : s) {if (f) os << ", ";f = true;os << d;}return os << "}";}
template <class T> ostream& operator<<(ostream& os, const multiset<T>& s) {os << "{";bool f = false;for (auto d : s) {if (f) os << ", ";f = true;os << d;}return os << "}";}
template<class T, class U>ostream &operator<<(ostream &os, const map<T, U> &s) {bool f = false;os<<endl;for(auto p: s) {if(f) os<<endl;f = true;os<<p.first<<": "<<p.second;}return os<<endl;}
void out() { cout << endl; }
template <class Head, class... Tail> void out(const Head &head, const Tail &...tail) {cout << head;if(sizeof...(tail)) cout << ' ';out(tail...);}

#ifdef LOCAL
template<typename T>ostream &operator<<(ostream &s, const vector<vector<T>> &vv) {int len=vv.size();for(int i=0; i<len; ++i) {if(i==0)s<<endl;s<<i<<":"<<vv[i];if(i!=len-1)s<<endl;}return s;}
struct PrettyOS {ostream& os;bool first;template <class T> auto operator<<(T&& x) {if (!first) os << ", ";first = false;os << x;return *this;}};
template <class... T> void dbg0(T&&... t) {(PrettyOS{cerr, true} << ... << t);}
#define dbg(...)do {cerr << #__VA_ARGS__ << ":  ";dbg0(__VA_ARGS__);cerr << endl;} while (false);
#else
#define dbg(...)
#endif

void vizGraph(VV &g, int directed = 0, int index = 0, string filename = "out.png") {
    #ifdef LOCAL
    ofstream ofs("./out.dot");
    ofs<<"digraph graph_name {"<<endl;
    set<P> memo;
    rep(i, g.size()) {
        rep(j, g[i].size()) {
            if(!directed && (memo.count(P(i, g[i][j])))) {
                continue;
            }
            //逆のみ出力しない
            memo.insert(P(g[i][j],i));
            ofs<<"    "<<i+index<<" -> "<<g[i][j]+index<<(!directed ? " [arrowhead = none]" : "")<<endl;
        }
        if(g[i].empty()){
            ofs<<"    "<<i+index<<endl;
        }
    }
    ofs<<"}"<<endl;
    ofs.close();
    system(((string) "dot -T png out.dot >"+filename).c_str());
    #else
    #endif
}

void vizGraphWithValue(VV &g, Vec &dp, int directed = 0, int index = 0, string filename = "out.png") {
    #ifdef LOCAL
    ofstream ofs("./out.dot");
    ofs<<"digraph graph_name {"<<endl;
    set<P> memo;
    auto node = [](ll ind, ll dp)->string {
        return '"'+to_string(dp)+"("+to_string(ind)+")"+'"';
    };
    rep(i, g.size()) {
        rep(j, g[i].size()) {
            if(!directed && memo.count(P(i, g[i][j]))) {
                continue;
            }
            memo.insert(P(g[i][j],i));
            ofs<<"    "<<node(i+index, dp[i])<<" -> "<<node(g[i][j]+index, dp[g[i][j]])<<(!directed ? " [arrowhead = none]" : "")
               <<endl;
        }
        if(g[i].empty()){
            ofs<<"    "<<node(i+index, dp[i])<<endl;
        }
    }
    ofs<<"}"<<endl;
    ofs.close();
    system(((string) "dot -T png out.dot >"+filename).c_str());
    #else
    #endif
}

void vizWeightedGraph(VVP &g, int directed = 0, int index = 0, string filename = "out.png") {
    #ifdef LOCAL
    ofstream ofs("./out.dot");
    ofs<<(directed ? "di" : "")<<"graph graph_name {"<<endl;
    string arrow = (directed ? " -> " : " -- ");
    set<P> used;
    rep(i, g.size()) {
        if(g[i].empty()){
            ofs<<"    "<<i+index<<endl;
            continue;
        }
        rep(j, g[i].size()) {
            if(used.count(mp(i, g[i][j].fi))) continue;
            if(directed == 0) used.insert(pair<int, int>(g[i][j].fi, i));
            ofs<<"    "<<i+index<<arrow<<g[i][j].fi+index;
            // 重みや容量があるならそれも出力
            ofs<<" [ label = \""<<g[i][j].se<<"\"];";
            ofs<<endl;
        }
    }
    ofs<<"}"<<endl;
    ofs.close();
    system(((string) "dot -T png out.dot >"+filename).c_str());
    #else
    #endif
}

void vizWeightedGraphWithValue(VVP &g,  Vec &dp, int directed = 0, int index = 0, string filename = "out.png") {
    #ifdef LOCAL
    ofstream ofs("./out.dot");
    ofs<<(directed ? "di" : "")<<"graph graph_name {"<<endl;
    string arrow = (directed ? " -> " : " -- ");
    set<P> used;
    auto node = [](ll ind, ll dp)->string {
        return '"'+to_string(dp)+"("+to_string(ind)+")"+'"';
    };
    rep(i, g.size()) {
        if(g[i].empty()){
            ofs<<"    "<<i+index<<endl;
            continue;
        }
        rep(j, g[i].size()) {
            if(used.count(mp(i, g[i][j].fi))) continue;
            if(directed == 0) used.insert(pair<int, int>(g[i][j].fi, i));
            ofs<<"    "<<node(i+index, dp[i])<<arrow<<node(g[i][j].fi+index, dp[g[i][j].fi]);
            // 重みや容量があるならそれも出力
            ofs<<" [ label = \""<<g[i][j].se<<"\"];";
            ofs<<endl;
        }
    }
    ofs<<"}"<<endl;
    ofs.close();
    system(((string) "dot -T png out.dot >"+filename).c_str());
    #else
    #endif
}

template<typename T=ll>
struct Zip {
    bool initialized;
    vector<T> v;
    Zip() : initialized(false) {}
    void add(T x) { v.push_back(x); }

    void init() {
        sort(ALL(v));
        Uniq(v);
        initialized = true;
    }

    ll id(T x) {
        if(!initialized) init();
        return lb(v, x);
    }

    T operator[](ll i) {
        if(!initialized) init();
        return v[i];
    }

    ll size() {
        if(!initialized) init();
        return v.size();
    }
};


#ifdef  LOCAL
template<typename T>void qdbg(queue<T> Q){while(!Q.empty()){T &x = Q.front();Q.pop();cerr<<x<<" ";;}cerr<<endl;}
template<typename T>void qdbg(deque<T> Q){while(!Q.empty()){T &x = Q.front();Q.pop_front();cerr<<x<<" ";;}cerr<<endl;}
template<typename T, typename U, typename V>void qdbg(priority_queue<T,U,V> Q){while(!Q.empty()){T x = Q.top();Q.pop();cerr<<x<<" ";;}cerr<<endl;}
#else
template<typename T>void qdbg(queue<T> &q){}
template<typename T>void qdbg(deque<T> &q){}
template<typename T, typename U, typename V>void qdbg(priority_queue<T,U,V> &q){}
#endif

int solve(){
    ll n;
    cin>>n;
    ll k;
    cin>>k;
    VP vp(n);
    cin>>vp;
    auto comp = [](P a, P b){
        if(a.fi == b.fi){
            return a.second < b.second;
        }else{
            return a.fi < b.fi;
        }
    };
    sort(ALL(vp),comp);
    VV g(n);
    //i番目の区間から紐付けられるものを考える

    Zip<ll> zip;
    rep(i,n){
        zip.add(vp[i].fi);
        zip.add(vp[i].se);
    }
    VVP event(2*n);
    VV ri(2*n);
    rep(i,n){
        auto [l,r] = vp[i];
        event[zip.id(l)].emplace_back(zip.id(r),i);
        ri[zip.id(r)].pb(i);
    }
    auto comp2 = [](P a, P b){
        return a.fi > b.fi;
    };
    priority_queue<P, VP, decltype(comp2)> pq(comp2);
    per(i,2*n-1){
        Each(p, event[i]){
            auto [r, id] = p;
            pq.emplace(r,id);
        }
        Each(v, ri[i]){
            if(!pq.empty()){
                //g[v].pb(pq.top().se);
                g[pq.top().se].pb(v);
            }
        }
    }

    Vec visited(n);
    dbg(g);
    deque<ll> q;
    ll ans = INF;
    ll len = 0;

    vizGraph(g);
    auto dfs = [&](auto &&self, ll i, ll p)->void {

        if(visited[i])return;
        visited[i] = 1;
        auto [l,r] = vp[i];
        q.pb(r - l);
        len += r - l;
        ll y = -1;
        ll z = -1;

        if(q.size() > 2 * k - 1){
            y = q.front();
            q.pop_front();
            z = q.front();
            q.pop_front();
            len -= y;
            len -= z;
        }

        dbg(i,len)
        qdbg(q);
        if(q.size() == 2 * k - 1){
            chmin(ans, len);
        }

        Each(nx, g[i]) {
            if(nx != p) {
                auto [nl, nr] = vp[nx];
                q.pb(l - nr);
                len += l - nr;
                self(self, nx, i);
                len -= l - nr;
                q.pop_back();
            }
        }

        if(z != -1){
            q.push_front(z);
            len += z;
        }
        if(y != -1){
            q.push_front(y);
            len += y;
        }

        q.pop_back();
        len -= r - l;
    };
    per(i,n-1){
        q.clear();
        dfs(dfs, i, -1);
    }
    outminusone(ans);
    return  0;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout<<std::setprecision(20);
//    ll T;
//    cin>>T;
//    while(T--)
    solve();
}