#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int N, X[250009], Y[250009];
vector<int> idx[100];

int main() {
	cin >> N;
	for (int i = 1; i <= N; i++) {
		cin >> X[i] >> Y[i];
		int t1 = X[i] % 9, t2 = Y[i] % 10;
		idx[t1 * 10 + t2].push_back(i);
	}

	pair<int, int> maxn = make_pair(-1, -1);
	for (int i = 0; i < 90; i++) maxn = max(maxn, make_pair((int)idx[i].size(), i));

	cout << idx[maxn.second].size() << endl;
	for (int i = 0; i < idx[maxn.second].size(); i++) {
		if (i) cout << " "; cout << idx[maxn.second][i];
	}
	cout << endl;
	return 0;
}