#include <bits/stdc++.h>

struct FastIO {
	char buf[1500000];
	char *ptr = buf;
	void read() {
		int size;
		size = fread(buf, 1, sizeof(buf) - 1, stdin);
		buf[size] = '\0';
		ptr = buf;
	}
	FastIO () {
		read();
	}
	template<typename Integer> Integer read() {
		bool neg = false;
		Integer res = 0;
		while ((*ptr < '0' || *ptr > '9') && *ptr != '-') ptr++;
		if (*ptr == '-') neg = true, ptr++;
		while (*ptr >= '0' && *ptr <= '9') res = res * 10 + *ptr - '0', ptr++;
		return neg ? -res : res;
	}
} fastio;
#define ri fastio.read<int>
#define rs64 fastio.read<int64_t>


int main() {
	int n = ri();
	std::vector<std::pair<int, int> > hen[n];
	for (int i = 0; i < n; i++) {
		int a = ri() - 1;
		int b = ri() - 1;
		hen[a].push_back({b, i});
		hen[b].push_back({a, i});
	}
	
	int degree[n];
	for (int i = 0; i < n; i++) degree[i] = hen[i].size();
	bool ok[n];
	for (auto &i : ok) i = true;
	
	std::queue<int> que;
	for (int i = 0; i < n; i++) if (degree[i] == 1) que.push(i);
	while (que.size()) {
		int i = que.front();
		que.pop();
		degree[i] = 0;
		for (auto j : hen[i]) {
			ok[j.second] = false;
			if (degree[j.first] && --degree[j.first] == 1) que.push(j.first);
		}
	}
	
	std::vector<int> res;
	for (int i = 0; i < n; i++) if (ok[i]) res.push_back(i);
	printf("%d\n", (int) res.size());
	for (int i = 0; i < (int) res.size(); i++) {
		if (i) printf(" ");
		printf("%d", res[i] + 1);
	}
	puts("");
	return 0;
}