#ifndef LOCAL #define FAST_IO #endif // ============ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define OVERRIDE(a, b, c, d, ...) d #define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i) #define REP3(i, m, n) for (i32 i = (i32)(m); i < (i32)(n); ++i) #define REP(...) OVERRIDE(__VA_ARGS__, REP3, REP2)(__VA_ARGS__) #define PER(i, n) for (i32 i = (i32)(n) - 1; i >= 0; --i) #define ALL(x) begin(x), end(x) using namespace std; using u32 = unsigned int; using u64 = unsigned long long; using i32 = signed int; using i64 = signed long long; using f64 = double; using f80 = long double; template using Vec = vector; template bool chmin(T &x, const T &y) { if (x > y) { x = y; return true; } return false; } template bool chmax(T &x, const T &y) { if (x < y) { x = y; return true; } return false; } #ifdef INT128 using u128 = __uint128_t; using i128 = __int128_t; istream &operator>>(istream &is, i128 &x) { i64 v; is >> v; x = v; return is; } ostream &operator<<(ostream &os, i128 x) { os << (i64)x; return os; } istream &operator>>(istream &is, u128 &x) { u64 v; is >> v; x = v; return is; } ostream &operator<<(ostream &os, u128 x) { os << (u64)x; return os; } #endif [[maybe_unused]] constexpr i32 INF = 1000000100; [[maybe_unused]] constexpr i64 INF64 = 3000000000000000100; struct SetUpIO { SetUpIO() { #ifdef FAST_IO ios::sync_with_stdio(false); cin.tie(nullptr); #endif cout << fixed << setprecision(15); } } set_up_io; // ============ #ifdef DEBUGF #else #define DBG(x) (void) 0 #endif int main() { i32 n, k; cin >> n >> k; Vec> rs(n); REP(i, n) { cin >> rs[i].first >> rs[i].second; } sort(ALL(rs)); rs.emplace_back(INF, INF); i32 t = 20; Vec> db(t, Vec(n + 1, 0)); REP(i, t) { db[i][n] = INF; } PER(i, n) { db[0][i] = min(rs[i].second, db[0][i + 1]); } REP(i, 1, t) { PER(j, n) { i32 idx = (i32)(lower_bound(ALL(rs), pair(db[i - 1][j], 0)) - rs.begin()); db[i][j] = min(db[i][j + 1], db[i - 1][idx]); } } i32 ans = INF; REP(i, n) { i32 cur = rs[i].first; REP(j, t) { if (k & (1 << j)) { i32 idx = (i32)(lower_bound(ALL(rs), pair(cur, 0)) - rs.begin()); cur = db[j][idx]; } } if (cur != INF) { chmin(ans, cur - rs[i].first); } } if (ans == INF) { cout << -1 << '\n'; } else { cout << ans << '\n'; } }