#include <bits/stdc++.h>
using i64 = long long;
void solve() {
int n, m;
std::cin >> n >> m;
std::vector<std::vector<int>> e(n);
std::map<std::pair<int, int>, int> id, cnt;
for (int i = 0; i < m; i++) {
int u, v;
std::cin >> u >> v;
u--;
v--;
e[u].push_back(v);
e[v].push_back(u);
id[std::minmax(u, v)] = i;
cnt[std::minmax(u, v)]++;
}
std::vector<int> color(n, -1), p(n), dep(n);
p[0] = -1;
std::function<void(int)> dfs = [&](int u) {
for (int v : e[u]) {
if (color[v] == -1) {
p[v] = u;
dep[v] = dep[u] + 1;
color[v] = color[u] ^ 1;
dfs(v);
}
}
};
for (int i = 0; i < n; i++) {
if (color[i] == -1) {
color[i] = 0;
p[i] = -1;
dfs(i);
}
}
std::vector<int> f(n);
int badEdges = 0;
for (int u = 0; u < n; u++) {
for (int v : e[u]) {
if (dep[u] < dep[v] && p[v] != u) {
if (color[u] == color[v]) {
badEdges++;
f[v]++;
f[u]--;
} else {
f[v]--;
f[u]++;
}
}
}
}
std::vector<bool> vis(n);
dfs = [&](int u) {
vis[u] = true;
for (int v : e[u]) {
if (p[v] == u && !vis[v]) {
dfs(v);
f[u] += f[v];
}
}
};
for (int i = 0; i < n; i++) {
if (!vis[i]) {
dfs(i);
}
}
std::vector<int> ans;
if (badEdges == 1) {
for (auto [p, i] : id) {
if (color[p.first] == color[p.second] && cnt[std::minmax(p.first, p.second)] == 1) {
ans.push_back(i);
}
}
}
for (int i = 1; i < n; i++) {
if (f[i] == badEdges && cnt[std::minmax(p[i], i)] == 1) {
ans.push_back(id[std::minmax(p[i], i)]);
}
}
std::sort(ans.begin(), ans.end());
std::cout << ans.size() << "\n";
}
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int t = 1;
// std::cin >> t;
while (t--) {
solve();
}
return 0;
}
