#define ATCODER #define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using ld = long double; using pll = pair; using pdd = pair; //template using pq = priority_queue, greater>; #define FOR(i, a, b) for(ll i=(a); i<(b);i++) #define REP(i, n) for(ll i=0; i<(n);i++) #define ROF(i, a, b) for(ll i=(b-1); i>=(a);i--) #define PER(i, n) for(ll i=n-1; i>=0;i--) #define REPREP(i,j,a,b) for(ll i=0;i > #define VV2(type,n,m,val) vector< vector > val;val.resize(n);for(ll i;i #define VEC(type,n,val) vector val;val.resize(n) #define VL vector #define VVL vector< vector > #define VP vector< pair > #define SZ size() #define all(i) begin(i),end(i) #define SORT(i) sort(all(i)) #define BITI(i) (1<>i) & 1) != 0) #define ALLBIT(n) (ll(1)<v?v:n #define MP(a,b) make_pair(a,b) #define DET2(x1,y1,x2,y2) x1*y2-x2*y1 #define DET3(x1,y1,z1,x2,y2,z2,x3,y3,z3) x1*y2*z3+x2*y3*z1+x3*y1*z2-z1*y2*x3-z2*y3*x1-z3*y1*x2 #define INC(a) for(auto& v:a)v++; #define DEC(a) for(auto& v:a)v--; #define SQU(x) (x)*(x) #define L0 ll(0) #ifdef ATCODER #include using namespace atcoder; using mint = modint1000000007; using mint2 = modint998244353; #endif template vector read(size_t n) { vector ts(n); for (size_t i = 0; i < n; i++) cin >> ts[i]; return ts; } template void read_tuple_impl(TV&) {} template void read_tuple_impl(TV& ts) { get(ts).emplace_back(*(istream_iterator(cin))); read_tuple_impl(ts); } template decltype(auto) read_tuple(size_t n) { tuple...> ts; for (size_t i = 0; i < n; i++) read_tuple_impl(ts); return ts; } using val = ll; using func = ll; val op(val a, val b) { return min(a, b); } val e() { return 1e18; } //val mp(func f, val a) { // return MP(a.first + f * a.second, a.second); //} func comp(func f, func g) { return f + g; } func id() { return 0; } ll di[4] = { 1,0,-1,0 }; ll dj[4] = { 0,1,0,-1 }; ll si[4] = { 0,3,3,0 }; ll sj[4] = { 0,0,3,3 }; //ll di[4] = { -1,-1,1,1 }; //ll dj[4] = { -1,1,-1,1 }; ll di8[8] = { 0,-1,-1,-1,0,1,1,1 }; ll dj8[8] = { -1,-1,0,1,1,1,0,-1 }; ll s; bool f(val v) { return v <= s; } void solve() { ll n, k; cin >> n >> k; auto [l, r] = read_tuple(n); VP lr(n); REP(i, n) lr[i] = MP(l[i], r[i]); SORT(lr); segtree st(n); REP(i, n) st.set(i, lr[i].second); VVL p(n, vector(20, -1)); REP(i, n) { auto il = lower_bound(all(lr), MP(lr[i].second, 0LL)); if (il == lr.end()) continue; ll id = il - lr.begin(); ll mn = st.prod(id, n); ll l1 = id, r1 = n; while (l1 + 1 < r1) { ll m = (l1 + r1) / 2; ll mn1 = st.prod(id, m); if (mn == mn1) { r1 = m; } else { l1 = m; } } p[i][0] = l1; } REP(i, 19) { REP(v, n) { if (p[v][i] == -1) continue; p[v][i + 1] = p[p[v][i]][i]; } } ll ans = 1e18; k--; REP(v, n) { ll kk = k; ll now = v; PER(i, 20) { ll up = 1LL << i; if (kk >= up) { now = p[now][i]; kk -= up; } if (now == -1) break; } if (now == -1) continue; CHMIN(ans, lr[now].second - lr[v].first); } if (ans > 1e17) ans = -1; cout << ans; return; } int main() { ll t = 1; ///cin >> t; while (t--) { solve(); } return 0; }