#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstring>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <cstdint>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
#define MP make_pair
#define PB push_back
#define inf 1000000007
#define rep(i,n) for(int i = 0; i < (int)(n); ++i)
#define all(x) (x).begin(),(x).end()

template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}
 
template<class T> inline bool chmax(T &a, T b){
    if(a<b){
        a = b;
        return true;
    }
    return false;
}

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

template<typename T> class segtree {
private:
    int n,sz,h; vector<T> node, lazy;
    vector<bool> lazyFlag;
    void eval(int k) {
        if(lazyFlag[k]){
            node[k] = lazy[k];
            if(k < n) {
                lazy[k*2] = lazy[k*2+1] = lazy[k];
                lazyFlag[k*2] = lazyFlag[k*2+1] = true;
            }
            lazyFlag[k] = false;
        }
    }

public:
    segtree(const vector<T>& v) : n(1), sz((int)v.size()), h(0){
        while(n < sz) n *= 2, h++;
        node.resize(2*n, numeric_limits<T>::max());
        lazy.resize(2*n); lazyFlag.resize(2*n, false);
        for(int i = 0; i < sz; i++) node[i+n] = v[i];
        for(int i = n - 1; i >= 1; i--) node[i] = min(node[i*2], node[i*2+1]);
    }
    void range(int a, int b, T x, int k=1, int l=0, int r=-1){
        if(r < 0) r = n;
        eval(k);
        if(b <= l || r <= a) return;
        if(a <= l && r <= b){
            lazy[k] = x, lazyFlag[k] = true; eval(k);
        }else{
            range(a, b, x, 2*k, l, (l+r)/2);
            range(a, b, x, 2*k+1, (l+r)/2, r);
            node[k] = min(node[2*k], node[2*k+1]);
        }
    }
    T query(int a, int b) {
        a += n, b += n - 1;
        for(int i = h; i > 0; i--) eval(a >> i), eval(b >> i);
        b++;
        T res1 = numeric_limits<T>::max(), res2 = numeric_limits<T>::max();
        while(a < b) {
            if(a & 1) eval(a), res1 = min(res1, node[a++]);
            if(b & 1) eval(--b), res2 = min(res2, node[b]);
            a >>= 1, b >>= 1;
        }
        return min(res1, res2);
    }
    void print(){for(int i = 0; i < sz; i++) cout<<query(i,i+1)<< " ";cout<<endl;}
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,m;
    cin >> m >> n;
    vector<int> aa(n);
    vector<int> bb(n);
    rep(i,n){
        bb[i] = -i;
    }
    segtree<int> sg(aa);
    segtree<int> sg2(bb);
    rep(i,m){
        int a,b;
        cin >> a >> b;
        a--;b--;
        int k = sg2.query(a,b+1);
        int nxt = k + (b+1);
        if(b<n-1){
            if(sg.query(b+1,b+2) > nxt){
                sg.range(b+1,b+2,nxt);
                sg2.range(b+1,b+2,nxt-(b+1));
            }
        }
        sg2.range(a,b+1,inf);
        sg.range(a,b+1,inf);
        int res = sg.query(0,n);
        if(res>=inf-1000000){
            cout << -1 << "\n";
        }else{
            cout << res + i+1 << "\n";
        }
    }
    return 0;
}

Measured memory_bytes: 12524