#include <bits/stdc++.h>
using namespace std;
#define LOCAL
#pragma region Macros
typedef long long ll;
#define ALL(x) (x).begin(),(x).end()
const long long MOD=1e9+7;
// const long long MOD=998244353;
const int INF=1e9;
const long long IINF=1e18;
const int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
const char dir[4]={'D','R','U','L'};

template<typename T>
istream &operator>>(istream &is,vector<T> &v){
    for (T &x:v) is >> x;
    return is;
}
template<typename T>
ostream &operator<<(ostream &os,const vector<T> &v){
    for (int i=0;i<v.size();++i){
        os << v[i] << (i+1==v.size()?"": " ");
    }
    return os;
}
template<typename T,typename U>
ostream &operator<<(ostream &os,const pair<T,U> &p){
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template<typename T,typename U>
ostream &operator<<(ostream &os,const map<T,U> &m){
    os << '{';
    for (auto itr=m.begin();itr!=m.end();++itr){
        os << '(' << itr->first << ',' << itr->second << ')';
        if (++itr!=m.end()) os << ',';
        --itr;
    }
    os << '}';
    return os;
}
template<typename T>
ostream &operator<<(ostream &os,const set<T> &s){
    os << '{';
    for (auto itr=s.begin();itr!=s.end();++itr){
        os << *itr;
        if (++itr!=s.end()) os << ',';
        --itr;
    }
    os << '}';
    return os;
}

void debug_out(){cerr << '\n';}
template<class Head,class... Tail>
void debug_out(Head&& head,Tail&&... tail){
    cerr << head;
    if (sizeof...(Tail)>0) cerr << ", ";
    debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...) cerr << " ";\
cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << '\n';\
cerr << " ";\
debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template<typename T> T gcd(T x,T y){return y!=0?gcd(y,x%y):x;}
template<typename T> T lcm(T x,T y){return x/gcd(x,y)*y;}

template<class T1,class T2> inline bool chmin(T1 &a,T2 b){
    if (a>b){a=b; return true;} return false;
}
template<class T1,class T2> inline bool chmax(T1 &a,T2 b){
    if (a<b){a=b; return true;} return false;
}
#pragma endregion

template<typename Monoid,typename OperatorMonoid>
struct LazySegmentTree{
    typedef function<Monoid(Monoid,Monoid)> F;
    typedef function<Monoid(Monoid,OperatorMonoid)> G;
    typedef function<OperatorMonoid(OperatorMonoid,OperatorMonoid)> H;
    int n,hi;
    F f;
    G g;
    H h;
    Monoid id0;
    OperatorMonoid id1;
    vector<Monoid> dat;
    vector<OperatorMonoid> laz;
    LazySegmentTree(int n_,F f,G g,H h,Monoid id0,OperatorMonoid id1):
                    f(f),g(g),h(h),id0(id0),id1(id1){init(n_);}
    void init(int n_){
        n=1,hi=0;
        while(n<n_) n<<=1,++hi;
        dat.assign(n<<1,id0);
        laz.assign(n<<1,id1);
    }
    void build(const vector<Monoid> &v){
        for (int i=0;i<v.size();++i) dat[i+n]=v[i];
        for (int i=n-1;i;--i) dat[i]=f(dat[i<<1|0],dat[i<<1|1]);
    }
    inline Monoid reflect(int k){
        return laz[k]==id1?dat[k]:g(dat[k],laz[k]);
    }
    inline void propagate(int k){
        if (laz[k]==id1) return;
        laz[k<<1|0]=h(laz[k<<1|0],laz[k]);
        laz[k<<1|1]=h(laz[k<<1|1],laz[k]);
        dat[k]=reflect(k);
        laz[k]=id1;
    }
    inline void thrust(int k){
        for (int i=hi;i;--i) propagate(k>>i);
    }
    inline void recalc(int k){
        while(k>>=1) dat[k]=f(reflect(k<<1|0),reflect(k<<1|1));
    }
    void update(int a,int b,OperatorMonoid x){
        if (a>=b) return;
        thrust(a+=n),thrust(b+=n-1);
        for (int l=a,r=b+1;l<r;l>>=1,r>>=1){
            if (l&1) laz[l]=h(laz[l],x),++l;
            if (r&1) --r,laz[r]=h(laz[r],x);
        }
        recalc(a),recalc(b);
    }
    void set_val(int k,Monoid x){
        thrust(k+=n);
        dat[k]=x,laz[k]=id1;
        recalc(k);
    }
    Monoid query(int a,int b){
        if (a>=b) return id0;
        thrust(a+=n),thrust(b+=n-1);
        Monoid vl=id0,vr=id0;
        for (int l=a,r=b+1;l<r;l>>=1,r>>=1){
            if (l&1) vl=f(vl,reflect(l++));
            if (r&1) vr=f(reflect(--r),vr);
        }
        return f(vl,vr);
    }
    Monoid operator[](int i){return query(i,i+1);}
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int H,W; cin >> H >> W;
    vector<int> A(H),B(H);
    for (int i=0;i<H;++i) cin >> A[i] >> B[i],--A[i];

    auto f=[](int a,int b){return min(a,b);};
    auto g=[](int a,int x){return x!=-1?x:a;};
    auto h=[](int a,int b){return b;};
    LazySegmentTree<int,int> seg(W,f,g,h,INF,-1)
                            ,nseg(W,f,g,h,W,-1);
    vector<int> v(W,0);
    seg.build(v);
    iota(v.begin(),v.end(),0);
    nseg.build(v);

    auto find=[&](int a,int sign){
        int lb=-1,ub=W,mid;
        while(ub-lb>1){
            mid=(ub+lb)>>1;
            if (!sign) (nseg[mid]>=a?ub:lb)=mid;
            else (nseg[mid]<=a?lb:ub)=mid;
        }
        return !sign?ub:lb;
    };
    for (int i=0;i<H;++i){
        int l=find(A[i],0),r=find(B[i]-1,1);
        int now=seg[B[i]];
        if (~r&&B[i]<W) seg.set_val(B[i],min(now,B[i]-r));
        nseg.update(l,r+1,B[i]);
        seg.update(A[i],B[i],INF);
        int ans=seg.query(0,W);
        cout << (ans==INF?-1:ans+i+1) << '\n';
    }
}

Measured memory_bytes: 13768