Codeforces Round ＃390 (Div. 2) D. Fedor and coupons

#include<bits/stdc++.h>

using namespace std;

#define X first
#define Y second
#define eps 1e-2
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

#define int long long 
const int maxn = 3e5+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

int n,k;
int l[maxn],r[maxn];

struct node {
     
    int l, r, id; 
}; 

priority_queue<int> q;
bool cmp(node x,node y){
    
    return x.l<y.l;
}
node nd[maxn];
void solve(){
    
    scanf("%lld%lld",&n,&k);
    for(int i=1;i<=n;i++) {
    
        scanf("%lld%lld",&l[i],&r[i]);
        nd[i]={
    l[i],r[i],i};
    }
    sort(nd+1,nd+1+n,cmp);
    int res=0,L=-1,R=-1;
    for(int i=1;i<=n;i++){
    
        // cout<<nd[i].l<<" "<<nd[i].r<<endl;
        q.push(-nd[i].r);
        if(q.size()>k) q.pop();
        if(q.size()==k){
    
            int now=(-q.top())-nd[i].l+1;
            // cout<<now<<endl;
            if(res<now){
    
                res=now;
                L=nd[i].l;
                R=(-q.top());
            }
        }
    }
    cout<<res<<endl;
    // cout<<L<<" "<<R<<endl;
    if(res==0){
    
        for(int i=1;i<=k;i++) cout<<i<<" ";cout<<endl;
    }else{
    
        for(int i=1,j=1;i<=n&&j<=k;i++){
    
            if(nd[i].l<=L&&nd[i].r>=R){
    
                ++j;cout<<nd[i].id<<" ";
            }
        }cout<<endl;
    }

    
    return;
}

int32_t main()
{
    
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    
    // printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}