#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(unsigned int n) {
		if (n >= 100000) *outptr++ = '0' + n / 100000;
		if (n >= 10000) *outptr++ = '0' + n / 10000 % 10;
		if (n >= 1000) *outptr++ = '0' + n / 1000 % 10;
		if (n >= 100) *outptr++ = '0' + n / 100 % 10;
		if (n >= 10) *outptr++ = '0' + n / 10 % 10;
		*outptr++ = '0' + n % 10;
	}
} fastio;
#define ri fastio.read<int>
#define rs64 fastio.read<int64_t>



int main() {
	int n = ri();
	int degree[n];
	uint64_t xored[n];
	memset(degree, 0, sizeof(degree));
	memset(xored, 0, sizeof(xored));
	for (int i = 0; i < n; i++) {
		int a = ri() - 1;
		int b = ri() - 1;
		degree[a]++;
		degree[b]++;
		xored[a] ^= (uint64_t) i << 32 | b;
		xored[b] ^= (uint64_t) i << 32 | a;
	}
	
	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();
		if (degree[i] == 1) {
			int j_hen = xored[i] >> 32;
			int j = xored[i] & 0xFFFFFFFF;
			ok[j_hen] = false;
			xored[j] ^= (uint64_t) j_hen << 32 | i;
			if (--degree[j] == 1) que.push(j); 
		}
	}
	
	std::vector<int> res;
	for (int i = 0; i < n; i++) if (ok[i]) res.push_back(i);
	
	fastio.put((unsigned int) res.size());
	fastio.put('\n');
	for (int i = 0; i < (int) res.size(); i++) {
		if (i) fastio.put(' ');
		fastio.put((unsigned int) res[i] + 1);
	}
	fastio.put('\n');
	return 0;
}