#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)
using ll = long long;
#define all(p) p.begin(),p.end()

int main(){
	int N;
	cin>>N;
	vector<vector<int>> p(90);
	rep(i,0,N){
		int x,y;
		cin>>x>>y;
		int A=(x%9)*10+(x*5+y)%10;
		p[A].push_back(i+1);
	}
	for(auto x:p){
		if(N<=90*(int)(x.size())){
			cout<<x.size()<<"\n";
			rep(i,0,(int)x.size()){
				if(i) cout<<" ";
				cout<<x[0];
			}
			cout<<"\n";
			return 0;
		}
	}
	assert(false);
}