BZOJ 4723: [POI2017]Flappy Bird

/**************************************************************
    Problem: 4723
    User: BeiYu
    Language: C++
    Result: Accepted
    Time:1884 ms
    Memory:1284 kb
****************************************************************/
 
#include <cstdio>
#include <iostream>
using namespace std;
 
#define debug(a) cout<<#a<<"="<<a<<" "
 
int n,m,ans;
int X,L,R;
 
int main(){
//  freopen("in.in","r",stdin);
    ios::sync_with_stdio(false);
     
    cin>>n>>m;
     
    X=L=R=0;
     
    for(int i=1;i<=n;i++){
        int x,l,r,t;
        cin>>x>>l>>r;
        l++,r--;
         
        t=(x-X);
         
        l=max(l,L-t);
        r=min(r,R+t);
         
        if((l-L+t)&1) l++;
        if((r-R+t)&1) r--;
         
        if(L<l-t) ans+=(l-t-L)>>1,L=l-t;
        if(R>r+t) R=r+t;
         
         
         
        if(L>R) return puts("NIE"),0;
         
        ans+=(l-L+t)>>1;
         
//      cout<<"-----------------"<<i<<"-------------------"<<endl;
//      debug(X),debug(L),debug(R)<<endl;
//      debug(x),debug(l),debug(r)<<endl;
//      debug(t),debug(((l-L+t)>>1))<<endl;
         
        L=l;
        R=r;
        X=x;
         
         
        if(L>R) return puts("NIE"),0;
    }
    cout<<ans<<endl;
    return 0;
}