#include <bits/stdc++.h>
using namespace std;
const int MaxN=2e5;
const int MaxA=2e5;
 
vector<int> pos[MaxA+1];
int add[MaxA+1]={};
int tag[MaxA+1];
 
int main() {
	int N, t, x;
	cin>>N;
	for(int n=1; n<=N; n++){
		cin>>t>>x;
		if(t==1){
			pos[x].push_back(n);
		}else{
			if(pos[x].empty()){
				cout<<-1;
				return 0;
			}
		}
		add[n]-=1;
		add[pos[x].back()]++;
		pos[x].pop_back();
	}
	//差分
	int ans=0;
	int now=0;
	for(int n=1; n<=N; n++){
		now+=add[n];
		ans=max(ans,now);
	}
	cout<<ans<<"\n";
	for(int n=1; n<=N; n+=1)
		if( -1<tag[n] )
			cout<<tag[n]<<" ";
	return 0;
}

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MTMKMSAyCjEgMwoxIDEKMSAzCjEgMgoyIDMKMSAzCjEgMwoyIDMKMSAzCjIgMgoyIDMKMiAxCg==

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