#include<bits/stdc++.h>
#define Gc() getchar() 
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;using LL=__uint128_t;
const int N=2e5+5,M=N*8+5,K=600+5,mod=998244353,Mod=mod-1;const db eps=1e-6;const int INF=1e9+7;mt19937 rnd(263082);
int n,m;
priority_queue<pii > q[N];
set<pii> Q;
namespace Tree{
	#define ls v<<1
	#define rs v<<1|1
	int f[M],g[M];
	void Up(int v){f[v]=min(f[ls],f[rs])-g[v];}
	void BD(int l=1,int r=2*n,int v=1){
		f[v]=m;if(l==r) return;int m=l+r>>1;
		BD(l,m,ls);BD(m+1,r,rs);
	}
	void Add(int x,int y,int l=1,int r=2*n,int v=1){
		if(x<=l&&r<=y) {g[v]++;f[v]--;return;}int m=l+r>>1;
		x<=m&&(Add(x,y,l,m,ls),0);y>m&&(Add(x,y,m+1,r,rs),0);Up(v);
	}
	int qry(int x,int y,int l=1,int r=2*n,int v=1){
		if(x<=l&&r<=y) return f[v];int m=l+r>>1;
		return min(x<=m?qry(x,y,l,m,ls):INF,y>m?qry(x,y,m+1,r,rs):INF)-g[v];
	}
	#undef ls
	#undef rs
}
void Del(int x){
	if(!q[x].empty()) Q.erase(make_pair(q[x].top().fi,x));
}
void Ins(int x){
	if(!q[x].empty()) Q.emplace(q[x].top().fi,x);
}
void Solve(){
	int i,j;scanf("%d%d",&n,&m);
	vector<int> ans;
	int Ct=1;
	Tree::BD();
	for(i=1;i<=2*n;i++){
		int x;if(i<=n) scanf("%d",&x);else x=-1;
		if(~x){Del(x);q[x].emplace(Ct,i);Ins(x);continue;}
		vector<int> E;
		while(!Q.empty()){
			auto p=*Q.rbegin();Q.erase(p);
			if(!Tree::qry(p.fi,Ct)) break;
			E.emplace_back(p.se);ans.emplace_back(q[p.se].top().se);q[p.se].pop();
			Tree::Add(p.fi,Ct);
		}
		for(int j:E) Ins(j);
		++Ct;
	}
	printf("%d\n",ans.size());
	for(int i:ans) printf("%d ",i);
}
int main(){
	int t=1;
	// scanf("%d",&t);
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}