#include <bits/stdc++.h>

template <typename T, typename = void>
struct is_iterable : std::false_type {};
template <typename T>
struct is_iterable<T, std::void_t<decltype(std::begin(std::declval<T>())),
                                  decltype(std::end(std::declval<T>()))>>
    : std::true_type {};

template <typename T, typename = void>
struct is_pair : std::false_type {};
template <typename T>
struct is_pair<T, std::void_t<decltype(std::declval<T>().first),
                              decltype(std::declval<T>().second)>>
    : std::true_type {};

template <typename T>
void debug(const T& v) {
  if constexpr (is_pair<T>::value) {
    std::cerr << "{";
    debug(v.first);
    std::cerr << ", ";
    debug(v.second);
    std::cerr << "}";
  } else if constexpr (is_iterable<T>::value &&
                       !std::is_same<T, std::string>::value) {
    std::cerr << "{";
    for (auto it = std::begin(v); it != std::end(v); ++it) {
      if (it != std::begin(v)) std::cerr << ", ";
      debug(*it);
    }
    std::cerr << "}";
  } else {
    std::cerr << v;
  }
}
template <typename T, typename... Ts>
void debug(const T& value, const Ts&... args) {
  debug(value);
  std::cerr << ", ";
  debug(args...);
}
#if DEBUG
#define dbg(...)                        \
  do {                                  \
    cerr << #__VA_ARGS__ << ": ";       \
    debug(__VA_ARGS__);                 \
    cerr << " (L" << __LINE__ << ")\n"; \
  } while (0)
#else
#define dbg(...)
#endif

void read_from_cin() {}
template <typename T, typename... Ts>
void read_from_cin(T& value, Ts&... args) {
  std::cin >> value;
  read_from_cin(args...);
}
#define rd(type, ...) \
  type __VA_ARGS__;   \
  read_from_cin(__VA_ARGS__);
#define ints(...) rd(int, __VA_ARGS__);
#define strings(...) rd(string, __VA_ARGS__);

template <typename T>
void write_to_cout(const T& value) {
  if constexpr (std::is_same<T, bool>::value) {
    std::cout << (value ? "Yes" : "No");
  } else {
    std::cout << value;
  }
}
template <typename T, typename... Ts>
void write_to_cout(const T& value, const Ts&... args) {
  write_to_cout(value);
  std::cout << ' ';
  write_to_cout(args...);
}
#define wt(...)                 \
  do {                          \
    write_to_cout(__VA_ARGS__); \
    cout << '\n';               \
  } while (0)

#define all(x) (x).begin(), (x).end()

#define rep_dispatch(_1, _2, _3, name, ...) name

#define rep3(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep2(i, n) rep3(i, 0, n)
#define rep1(n) rep2(_loop_variable_, n)
#define rep(...) rep_dispatch(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)

#define rrep3(i, a, b) for (int i = (int)(b)-1; i >= a; --i)
#define rrep2(i, n) rrep3(i, 0, n)
#define rrep1(n) rrep2(_loop_variable_, n)
#define rrep(...) rep_dispatch(__VA_ARGS__, rrep3, rrep2, rrep1)(__VA_ARGS__)

template <typename T>
std::istream& operator>>(std::istream& is, std::vector<T>& v) {
  for (T& vi : v) is >> vi;
  return is;
}

template <typename T, typename U>
std::istream& operator>>(std::istream& is, std::pair<T, U>& p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T, typename U>
bool chmax(T& a, U b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T, typename U>
bool chmin(T& a, U b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T>
int sz(const T& v) {
  return v.size();
}

template <typename T>
int popcount(T i) {
  return std::bitset<std::numeric_limits<T>::digits>(i).count();
}

#include <boost/hana/functional/fix.hpp>
const auto& Fix = boost::hana::fix;

using ll = long long;

template <typename T>
using low_priority_queue =
    std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <typename T>
using V = std::vector<T>;
template <typename T>
using VV = V<V<T>>;

using namespace std;

struct S {
  int begin, end;
  optional<int> value;
  bool flat;
  bool operator<(const S& s) const { return begin < s.begin; }
};

ostream& operator<<(ostream& os, const S& s) {
  os << "{" << s.begin << "," << s.end << ","
     << (s.value ? to_string(*s.value) : "{}") << "," << s.flat << "}";
  return os;
}

int main() {
  ints(h, w);
  V<int> a(h), b(h);
  rep(i, h) {
    cin >> a[i] >> b[i];
    --a[i];  // [a, b)
  }

  set<S> s{{0, w, {0}, true}};
  multiset<int> ms{0};

  rep(i, h) {
    auto it = s.lower_bound(S{a[i], 0, 0, false});
    auto lt = it;
    if (lt == s.end() || lt->begin > a[i]) --lt;
    assert(lt->begin <= a[i] && a[i] < lt->end);
    auto rt = s.lower_bound(S{b[i], 0, 0, false});
    if (rt == s.end()) --rt;
    if (rt->begin >= b[i]) --rt;
    if (rt->end < b[i]) ++rt;
    dbg(a[i], b[i]);
    dbg(*rt);
    assert(rt->begin < b[i] && b[i] <= rt->end);

    V<S> todo;
    if (lt->begin < a[i]) {
      S s = *lt;
      s.end = a[i];
      todo.push_back(s);
    }
    if (b[i] < rt->end) {
      S s = *rt;
      if (s.value) {
        if (!s.flat) {
          *s.value += b[i] - s.begin;
        }
      }
      s.begin = b[i];
      todo.push_back(s);
    }
    for (auto it = lt; it != next(rt); ++it) {
      if (it->value) {
        ms.erase(ms.find(*it->value));
      }
    }
    s.erase(lt, next(rt));
    for (auto& t : todo) {
      s.insert(t);
      if (t.value) {
        ms.insert(*t.value);
      }
    }
    auto [nt, ok] = s.insert(S{a[i], b[i], nullopt, false});
    assert(ok);
    if (nt != s.begin()) {
      auto pt = prev(nt);
      if (pt->value) {
        const_cast<S&>(*nt).value =
            *pt->value + (pt->flat ? 1 : (pt->end - pt->begin));
        ms.insert(*nt->value);
      }
    }
    dbg(s);
    dbg(ms);
    if (ms.empty()) {
      wt(-1);
    } else {
      wt(*ms.begin() + i + 1);
    }
  }
}


Measured memory_bytes: 17136