#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> pi;
vector<pi> AdjList[100005];
int colour[100005], visit[100005], depth[100005];
int badup[100005], goodup[100005];
int badlow[100005], goodlow[100005];
int badlep[100005], goodlep[100005];
int baduep[100005], gooduep[100005];
int par[100005];
int N, M, A, B;
int total_bad = 0;
int usable = 0;
void dfs(int x, int p){
par[x] = p;
//cout << x << ' ' << p << '\n';
visit[x] = 1;
for (auto it : AdjList[x]){
int v = it.first, e = it.second;
if (e == p) continue;
if (visit[v]){
if (depth[x] > depth[v]){
if (colour[x] == colour[v]){
badlep[x]++;
badup[x]++;
baduep[v]++;
total_bad++;
}
else{
goodlep[x]++;
goodup[x]++;
gooduep[v]++;
}
}
}
else{
depth[v] = depth[x] + 1;
colour[v] = 1 - colour[x];
dfs(v,e);
badup[x] += badup[v];
goodup[x] += goodup[v];
}
}
badup[x] -= baduep[x];
goodup[x] -= gooduep[x];
}
void check_vertex(int x, int p){
visit[x] = 1;
//cout << "CHECKING " << x << ' ' << p << '\n';
if (p != -1){
if (total_bad == badup[x]){
if (goodup[x] == 0){
usable++;
//cout << p << " CASE 1A\n";
}
}
}
for (auto it : AdjList[x]){
int v = it.first, e = it.second;
if (p == e) continue;
if (par[v] == e){
check_vertex(v,e);
}
else{
if (depth[x] < depth[v]) continue;
if (total_bad == 1 && colour[v] == colour[x]){
usable++;
//cout << "CASE 2A\n";
}
}
}
//cout << "ENDING " << x << ' ' << p << '\n';
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> N >> M;
for (int i = 1; i <= M; ++i){
cin >> A >> B;
AdjList[A].push_back(pi(B,i));
AdjList[B].push_back(pi(A,i));
}
for (int i = 1; i <= N; ++i){
if (!visit[i]){
depth[i] = 0;
colour[i] = 0;
dfs(i,-1);
}
}
for (int i = 1; i <= N; ++i){
visit[i] = 0;
}
for (int i = 1; i <= N; ++i){
if (!visit[i]){
check_vertex(i,-1);
}
}
/*
for (int i = 1; i <= N; ++i){
cout << badup[i] << ' ' << goodup[i] << '\n';
}
*/
cout << usable << '\n';
}
