#include <bits/stdc++.h>

struct FastIO {
	char inbuf[1500000];
	char outbuf[800000];
	char *inptr = inbuf;
	char *outptr = outbuf;
	void read() {
		int size = fread(inbuf, 1, sizeof(inbuf) - 1, stdin);
		inbuf[size] = '\0';
		inptr = inbuf;
	}
	FastIO () {
		read();
	}
	~FastIO() {
		fwrite(outbuf, 1, outptr - outbuf, stdout);
	}
	template<typename Integer> Integer read() {
		bool neg = false;
		Integer res = 0;
		while ((*inptr < '0' || *inptr > '9') && *inptr != '-') inptr++;
		if (*inptr == '-') neg = true, inptr++;
		while (*inptr >= '0' && *inptr <= '9') res = res * 10 + *inptr - '0', inptr++;
		return neg ? -res : res;
	}
	void put(char c) { *outptr++ = c; }
	void put(int n) {
		static char tmp[10];
		if (!n) {
			put('0');
			return;
		}
		if (n < 0) n = -n, put('-');
		
		char *tmpptr = tmp;
		while (n) *tmpptr++ = n % 10 + '0', n /= 10;
		while (tmpptr != tmp) *outptr++ = *--tmpptr;
	}
} 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);
	
	fastio.put((int) res.size());
	fastio.put('\n');
	for (int i = 0; i < (int) res.size(); i++) {
		if (i) fastio.put(' ');
		fastio.put(res[i] + 1);
	}
	fastio.put('\n');
	return 0;
}