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

using ll = long long;
#define endl '\n'
#define rep(i, n) for (long long i = 0; i < (n); ++i)
#define repr(i, a, b) for (auto i = (a); i < (b); ++i)
#define itr(x) for (auto&& v : (x))
#define updatemax(t, v) ((t) = std::max((t), (v)))
#define updatemin(t, v) ((t) = std::min((t), (v)))

#include <boost/concept_check.hpp>
#include <functional>
#include <vector>

template <
    typename T,
    typename F,
    typename LazyT = T,
    typename LazyApply = T (*)(const T&, const LazyT&, int, int),
    typename LazyAdd = LazyT (*)(const LazyT&, const LazyT&)>
class segtree {
  BOOST_CLASS_REQUIRE2(F, std::function<T(T&, T&)>, boost, ConvertibleConcept);
  BOOST_CLASS_REQUIRE2(LazyApply, std::function<T(T&, LazyT&, int, int)>, boost, ConvertibleConcept);
  BOOST_CLASS_REQUIRE2(LazyAdd, std::function<LazyT(LazyT&, LazyT&)>, boost, ConvertibleConcept);

  const int n;
  const F f;
  const T fIdentity;
  const LazyApply lazyApply;
  const LazyAdd lazyAdd;

  std::vector<T> data;
  std::vector<LazyT> lazyData;
  std::vector<bool> lazyflag;

  int dataLength(int n) {
    int res = 2;
    while (res < n) res = res << 1;
    return res;
  }

  void recalcData(int p, int pBegin, int pEnd, bool recurseToTop = false) {
    data[p] = f(data[(p << 1) + 1], data[(p << 1) + 2]);
    if (lazyflag[p]) data[p] = lazyApply(data[p], lazyData[p], pBegin, pEnd);
    if (recurseToTop && p > 0) {
      int pSize = pEnd - pBegin;
      recalcData((p - 1) >> 1, p & 1 ? pBegin : pBegin - pSize, p & 1 ? pEnd + pSize : pEnd, true);
    }
  }

  void _updateLazy(int begin, int end, const LazyT& value, int p, int pBegin, int pEnd) {
    if (begin <= pBegin && pEnd <= end) {
      addLazyData(p, pBegin, pEnd, value);
    } else if (pBegin < end && begin < pEnd) {
      evalLazy(p, pBegin, pEnd);
      int pCenter = (pBegin + pEnd) >> 1;
      _updateLazy(begin, end, value, (p << 1) + 1, pBegin, pCenter);
      _updateLazy(begin, end, value, (p << 1) + 2, pCenter, pEnd);
      recalcData(p, pBegin, pEnd, false);
    }
  }

  void addLazyData(int p, int pBegin, int pEnd, const LazyT& value) {
    data[p] = lazyApply(data[p], value, pBegin, pEnd);
    lazyData[p] = lazyflag[p]
                      ? lazyAdd(lazyData[p], value)
                      : value;
    lazyflag[p] = true;
  }

  void evalLazy(int p, int pBegin, int pEnd) {
    if (!lazyflag[p]) return;
    int pCenter = (pBegin + pEnd) >> 1;
    addLazyData((p << 1) + 1, pBegin, pCenter, lazyData[p]);
    addLazyData((p << 1) + 2, pCenter, pEnd, lazyData[p]);
    lazyflag[p] = false;
  }

  T _calc(int begin, int end, int p, int pBegin, int pEnd) {
    if (begin <= pBegin && pEnd <= end) {
      return data[p];
    } else if (end <= pBegin || pEnd <= begin) {
      return fIdentity;
    } else {
      evalLazy(p, pBegin, pEnd);
      int pCenter = (pBegin + pEnd) >> 1;
      return f(
          _calc(begin, end, (p << 1) + 1, pBegin, pCenter),
          _calc(begin, end, (p << 1) + 2, pCenter, pEnd));
    }
  }

 public:
  segtree(
      int n,
      F f,
      T fIdentity,
      LazyApply lazyApply = nullptr,
      LazyAdd lazyAdd = nullptr,
      LazyT _someValueOfLazyT = LazyT() /* LazyT推論用 */)
      : n(dataLength(n)),
        f(f),
        fIdentity(fIdentity),
        lazyApply(lazyApply),
        lazyAdd(lazyAdd) {
    data.resize(2 * this->n - 1);
    lazyData.resize(2 * this->n - 1);
    lazyflag.resize(2 * this->n - 1);
    for (int i = 0; i < 2 * this->n - 1; ++i) data[i] = fIdentity;
  }

  void update(int index, const T& value) {
    int p = n + index - 1;
    data[p] = value;
    recalcData((p - 1) >> 1, index - 1 + (p & 1), index + 1 + (p & 1), true);
  }

  void updateLazy(int begin, int end, const LazyT& value) {
    _updateLazy(begin, end, value, 0, 0, n);
  }

  T operator()(int begin, int end) {
    return _calc(begin, end, 0, 0, n);
  }
};

int wl[200100], wr[200100];
int main() {
  cin.tie(nullptr), cout.tie(nullptr), ios::sync_with_stdio(false), cout.precision(16);
  ll h, w;
  cin >> h >> w;
  rep(i, h) {
    cin >> wl[i] >> wr[i];
    --wl[i];
  }
  ll inf = LLONG_MAX / 4;
  auto stf0 = [](const ll& a, const ll& b) { return min(a, b); };
  auto stf1 = [](const ll& a, const ll& b) { return max(a, b); };
  auto stf2 = [](const ll& x, const ll& y, int b, int e) { return y; };
  auto stf3 = [](const ll& x, const ll& y) { return y; };
  segtree st1(w, stf0, inf, stf2, stf3);
  segtree st2(w, stf1, -inf, stf2, stf3);
  rep(i, w) {
    st1.update(i, 0);
    st2.update(i, i);
  }
  rep(i, h) {
    if (wr[i] < w) {
      auto rp = st2(wl[i], wr[i] + 1);
      if (rp < w) {
        st2.updateLazy(wr[i], wr[i] + 1, rp);
        st1.updateLazy(wr[i], wr[i] + 1, wr[i] - rp);
      }
    }
    st1.updateLazy(wl[i], wr[i], inf);
    st2.updateLazy(wl[i], wr[i], -inf);
    auto ans = st1(0, w);
    cout << (ans < w ? ans + i + 1 : -1) << endl;
  }
}


Measured memory_bytes: 21492