#include<bits/stdc++.h>
using namespace std;
typedef long long ll;typedef double db;
typedef pair<int, int> pii;typedef pair<ll, ll> pll;
typedef pair<int,ll> pil;typedef pair<ll,int> pli;
#define Fi first
#define Se second
#define _Out(a)	cerr<<#a<<" = "<<(a)<<endl
const int INF = 0x3f3f3f3f, MAXN = 1e6 + 7;
const ll LINF = 0x3f3f3f3f3f3f3f3f, MOD = 1e9+7;
const db Pi = acos(-1), EPS = 1e-6;
void test(){cerr << "\n";}template<typename T,typename...Args>void test(T x,Args...args){cerr<<x<<" ";test(args...);}
inline ll qpow(ll a, ll b){return b?((b&1)?a*qpow(a*a%MOD,b>>1)%MOD:qpow(a*a%MOD,b>>1))%MOD:1;}
inline ll qpow(ll a, ll b,ll c){return b?((b&1)?a*qpow(a*a%c,b>>1,c)%c:qpow(a*a%c,b>>1,c)) %c:1;}
inline ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
inline ll cede(ll a,ll b){if(b<0)return cede(-a,-b);if(a<0)return a/b;return (a+b-1)/b;}
inline ll flde(ll a,ll b){if(b<0)return flde(-a,-b);if(a<0)return (a-b+1)/b;return a/b;}
inline int sign(db x){return x<-EPS ? -1:x>EPS;}
inline int dbcmp(db l,db r){return sign(l - r);}
namespace Fast_IO{ //orz laofu
    const int MAXL((1 << 18) + 1);int iof, iotp;
    char ioif[MAXL], *ioiS, *ioiT, ioof[MAXL],*iooS=ioof,*iooT=ioof+MAXL-1,ioc,iost[55];
    char Getchar(){
        if (ioiS == ioiT){
            ioiS=ioif;ioiT=ioiS+fread(ioif,1,MAXL,stdin);return (ioiS == ioiT ? EOF : *ioiS++);
        }else return (*ioiS++);
    }
    void Write(){fwrite(ioof,1,iooS-ioof,stdout);iooS=ioof;}
    void Putchar(char x){*iooS++ = x;if (iooS == iooT)Write();}
    inline int read(){
        int x=0;for(iof=1,ioc=Getchar();ioc<'0'||ioc>'9';)iof=ioc=='-'?-1:1,ioc=Getchar();
        for(x=0;ioc<='9'&&ioc>='0';ioc=Getchar())x=(x<<3)+(x<<1)+(ioc^48);return x*iof;
    }
    inline long long read_ll(){
        long long x=0;for(iof=1,ioc=Getchar();ioc<'0'||ioc>'9';)iof=ioc=='-'?-1:1,ioc=Getchar();
        for(x=0;ioc<='9'&&ioc>='0';ioc=Getchar())x=(x<<3)+(x<<1)+(ioc^48);return x*iof;
    }
    template <class Int>void Print(Int x, char ch = '\0'){
        if(!x)Putchar('0');if(x<0)Putchar('-'),x=-x;while(x)iost[++iotp]=x%10+'0',x/=10;
        while(iotp)Putchar(iost[iotp--]);if (ch)Putchar(ch);
    }
    void Getstr(char *s, int &l){
        for(ioc=Getchar();ioc <'a'||ioc>'z';)ioc=Getchar();
        for(l=0;ioc<='z'&&ioc>='a';ioc=Getchar())s[l++]=ioc;s[l] = 0;
    }
    void Putstr(const char *s){for(int i=0,n=strlen(s);i<n;++i)Putchar(s[i]);}
} // namespace Fast_IO
using namespace Fast_IO;

map<int,int>mp;
set<pii>st;
void work()
{
    int n=read(),m=read();
    for(int i=1;i<=m;i++)
    {
        mp[i]=0;st.insert({0,i});
    }

    for(int i=1;i<=n;i++)
    {
        int A=read(),B=read();
        int minv=INF;
        while(1)
        {
            auto it=mp.lower_bound(A);
            if(it==mp.end()||it->first>B)break;
            st.erase({it->second,it->first});
            minv=min(minv,it->second+B+1-(it->first));
            mp.erase(it);
        }
        if(B<m&&minv!=INF)
        {
            if(mp.count(B+1)&&mp[B+1]>minv)
            {
                st.erase({mp[B+1],B+1});
                mp[B+1]=minv;
                st.insert({minv,B+1});
            }else if(!mp.count(B+1)) 
            {
                mp[B+1]=minv;
                st.insert({minv,B+1});
            }
        }
        printf("%d\n",st.empty()?-1:i+st.begin()->first);
    }

    
}

int main()
{
    //std::ios::sync_with_stdio(false);
   // int T=read();for(int cas=1;cas<=T;cas++)
    //int T;scanf("%d",&T);for(int i=1;i<=T;i++)
    work();
    // Write();
}
/*
5 5
1 5
1 4
1 3
1 2
1 1
*/

Measured memory_bytes: 22688