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

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << "Line " << __LINE__ << ": " <<  #x << " = " << (x) << "\n";
#define spa << " " <<
#define fi first
#define se second
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()

using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<long, long>;
using pdd = pair<ld, ld>;

template<typename T> using V = vector<T>;
template<typename T> using P = pair<T, T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;

template <class T> void UNIQUE(vector<T> &x) {sort(ALL(x));x.erase(unique(ALL(x)), x.end());}
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<"\n";}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<"\n";};

const ll INF = (1ll<<62);
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const ll mod = (int)1e9 + 7;
//const ll mod = 998244353;

template< typename Monoid >
struct SegmentTree {
  using F = function< Monoid(Monoid, Monoid) >;

  int sz;
  vector< Monoid > seg;

  const F f;
  const Monoid M1;

  // n: 要素数，F: モノイド間の演算，M1: 演算の単位元
  // F は無名関数で渡す
  SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
    sz = 1;
    while(sz < n) sz <<= 1;
    seg.assign(2 * sz, M1);
  }

  // k番目の要素にxを代入
  void set(int k, const Monoid &x) {
    seg[k + sz] = x;
  }

  // 構築
  void build() {
    for(int k = sz - 1; k > 0; k--) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  // k番目の値をxに変更
  void update(int k, const Monoid &x) {
    k += sz;
    seg[k] = x;
    while(k >>= 1) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  // 区間[a, b)に関して演算して結果を返す
  Monoid query(int a, int b) {
    Monoid L = M1, R = M1;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) L = f(L, seg[a++]);
      if(b & 1) R = f(seg[--b], R);
    }
    return f(L, R);
  }

  // k番目の値を返す(set[k]でアクセス)
  Monoid operator[](const int &k) const {
    return seg[k + sz];
  }


  template< typename C >
  int find_subtree(int a, const C &check, Monoid &M, bool type) {
    while(a < sz) {
      Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
      if(check(nxt)) a = 2 * a + type;
      else M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }


  template< typename C >
  //[a, x)がcheckを満たす最初の要素位置xを返す
  // ↑嘘かも．[a, x]が正しい
  // 存在しない場合は-1を返すことに注意
  // Cには判定関数を入れる
  int find_first(int a, const C &check) {
    Monoid L = M1;
    if(a <= 0) {
      if(check(f(L, seg[1]))) return find_subtree(1, check, L, false);
      return -1;
    }
    int b = sz;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) {
        Monoid nxt = f(L, seg[a]);
        if(check(nxt)) return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }

  //[x, b)がcheckを満たす最後の要素位置xを返す
  template< typename C >
  int find_last(int b, const C &check) {
    Monoid R = M1;
    if(b >= sz) {
      if(check(f(seg[1], R))) return find_subtree(1, check, R, true);
      return -1;
    }
    int a = sz;
    for(b += sz; a < b; a >>= 1, b >>= 1) {
      if(b & 1) {
        Monoid nxt = f(seg[--b], R);
        if(check(nxt)) return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
};

int main(){

    ll H, W;
    cin >> H >> W;
    V<ll> A(H), B(H);
    REP(i, H) cin >> A[i] >> B[i];
    REP(i, H) A[i]--, B[i]--;

    auto print_set = [](set<pll> &st){
        for(auto x: st) cout << x << " ";
        cout << "\n";
    };

    auto print_seg  = [&](SegmentTree<ll> &seg){
        REP(i, W) cout << seg[i] << " ";
        cout << "\n";
    };

    SegmentTree<ll> seg(W, [](ll x, ll y){return min(x, y);}, INF);
    REP(i, W) seg.set(i, 0);
    seg.build();
    set<pll> st;
    REP(i, W){
        st.insert({i, i});
    }
    REP(t, H){
        auto itr = st.lower_bound({A[t], 0});
        // print_set(st);
        // print_seg(seg);
        while(1){
            if(itr == st.end()) break;
            ll en = itr->first;
            ll start = itr->second;
            if(en<=B[t]){
                if(next(itr) == st.end() or next(itr)->first > B[t]){
                    ll upd = (B[t] == W-1 ? INF : B[t] + 1);
                    itr = st.erase(itr);
                    st.insert({upd, start});
                    seg.update(start, upd-start);
                }else{
                    itr = st.erase(itr);
                    seg.update(start, INF);
                }
            }else{
                break;
            }
        }
        // print_set(st);
        // print_seg(seg);
        // dump(seg.query(0, W))
        // dump(t)
        // cout << "\n";
        cout << (seg.query(0, W) >= INF/2 ? -1 : seg.query(0, W) + t + 1) << "\n";
    }

    return 0;
}

Measured memory_bytes: 22932