#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int MAXN = 1e5;
int N, M, ans;
vector<int> adj[MAXN+10];
bool vis[MAXN+10];
int in[MAXN+10], out[MAXN+10], col[MAXN+10], root[MAXN+10], cnt;
vector<pii> odd, even;
void dfs(int now, int bef, int dep)
{
vis[now]=true;
col[now]=dep;
in[now]=++cnt;
int p=0;
for(int nxt : adj[now])
{
if(nxt==bef && p==0) { p++; continue; }
if(!vis[nxt]) dfs(nxt, now, 1-dep);
else
{
if(now<nxt) continue;
if(col[now]!=col[nxt]) odd.push_back({now, nxt});
else even.push_back({now, nxt});
}
}
out[now]=cnt;
}
struct BIT
{
int tree[MAXN+10];
BIT() { memset(tree, 0, sizeof(tree)); }
void update(int i) { for(; i<=N; i+=(i&-i)) tree[i]++; }
int query(int i) { int ret=0; for(; i>0; i-=(i&-i)) ret+=tree[i]; return ret; }
int query(int l, int r) { return query(r)-query(l-1); }
};
BIT bit1, bit2;
int main()
{
int i, j;
scanf("%d%d", &N, &M);
for(i=1; i<=M; i++)
{
int u, v;
scanf("%d%d", &u, &v);
adj[u].push_back(v);
adj[v].push_back(u);
}
for(i=1; i<=N; i++) if(!vis[i]) dfs(i, i, 0), root[i]=1;
//printf("ODD\n");
//for(auto it : odd) printf("%d %d\n", it.first, it.second);
//printf("EVEN\n");
//for(auto it : even) printf("%d %d\n", it.first, it.second);
for(auto &it : odd)
{
it.first=in[it.first]; it.second=in[it.second];
if(it.first>it.second) swap(it.first, it.second);
}
for(auto &it : even)
{
it.first=in[it.first]; it.second=in[it.second];
if(it.first>it.second) swap(it.first, it.second);
}
if(even.size()==1) ans++;
//printf("DFSN\n");
//for(i=1; i<=N; i++) printf("%d : %d %d\n", i, in[i], out[i]);
vector<pii> todo;
for(i=1; i<=N; i++)
{
if(root[i]) continue;
todo.push_back({in[i], out[i]});
}
sort(odd.begin(), odd.end());
sort(even.begin(), even.end());
sort(todo.begin(), todo.end());
i=0, j=0;
for(auto it : todo)
{
for(; i<odd.size() && odd[i].first<it.first; i++) bit1.update(odd[i].second);
for(; j<even.size() && even[j].first<it.first; j++) bit2.update(even[j].second);
if(bit1.query(it.first, it.second)==0 && bit2.query(it.first, it.second)==even.size()) ans++;
}
printf("%d\n", ans);
}
