#include<stdio.h>
#include<string>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
typedef pair<int, int> pii;
const int MX = 100005;
vector<pii> G[MX], B;
vector<int> T[MX];
int C[MX], P[20][MX], lev[MX];
int cnt, ans, cut[MX], con[MX];
void dfs(int x, int p)
{
for (pii cc : G[x]){
int &c = cc.first, &d = cc.second;
if (d == p) continue;
if (C[c] && x > c)B.push_back(pii(x, c));
else if( !C[c] ){
T[x].push_back(c);
P[0][c] = x; lev[c] = lev[x] + 1;
C[c] = 3 - C[x];
dfs(c, d);
}
}
}
pii solve(int x)
{
if (C[x] == 3) return pii(0, 0);
C[x] = 3;
pii tot = pii(cut[x], con[x]);
for (int c : T[x]){
pii t = solve(c);
tot.first += t.first;
tot.second += t.second;
}
if (tot.first == cnt && tot.second == 0) ans++;
return tot;
}
void up(int &x, int d)
{
if (d < 0) return;
for (int i = 0; d; i++, d /= 2){
if (d & 1) x = P[i][x];
}
}
int LCA(int A, int B)
{
up(A, lev[A] - lev[B]);
up(B, lev[B] - lev[A]);
for (int i = 0; i < 20; i++){
if (P[i][A] != P[i][B]) A = P[i][A], B = P[i][B];
}
if (A != B) return P[0][A];
else return A;
}
int main()
{
int N, M;
scanf("%d%d", &N, &M);
for (int i = 0; i < M; i++){
int X, Y;
scanf("%d%d", &X, &Y);
if (X == Y) for (;;);
G[X].push_back(pii(Y, i));
G[Y].push_back(pii(X, i));
}
for (int i = 1; i <= N; i++){
if (C[i]) continue;
C[i] = 1; lev[i] = 1;
dfs(i, -1);
}
for (int i = 1; i < 20; i++){
for (int j = 1; j <= N; j++){
P[i][j] = P[i - 1][P[i - 1][j]];
}
}
for (pii c : B){
int X = c.first, Y = c.second;
int p = LCA(X, Y);
if (C[X] == C[Y]){
cnt++;
cut[X]++, cut[Y]++, cut[p] -= 2;
}
else{
con[X]++, con[Y]++, con[p] -= 2;
}
}
if (cnt == 1) ans++;
for (int i = 1; i <= N; i++){
if (C[i] == 3) continue;
solve(i);
if (cnt == 0) ans--; // root
}
printf("%d", ans);
return 0;
}
