#include <bits/stdc++.h>
using namespace std;
struct E{ int x, i; };
int n, m, vis[100010], cr, d[100010], ps[100010], pe[100010], cnt, dc, fl, ans;
vector<E> e[100010];
vector<int> t[100010];
void T_T(){ puts("0"); exit(0); }
void col(int x, int c){
vis[x] = c;
for(auto &i : e[x]){
if(vis[i.x] && vis[i.x] != 3 - c) fl = 0;
else if(!vis[i.x]) col(i.x, 3 - c);
}
}
const int sz = 131072;
struct Seg{
int dat[2 * sz];
void upd(int x, int v){ for(x += sz; x; x /= 2) dat[x] += v; }
int get(int s, int e){
int ret = 0;
for(s += sz, e += sz; s <= e; s /= 2, e /= 2){
if(s % 2 == 1) ret += dat[s++];
if(e % 2 == 0) ret += dat[e--];
}
return ret;
}
} S[2];
void g(int x, int p){
vis[x] = 1;
ps[x] = ++cnt;
for(auto &i : e[x]){
if(i.i == p) continue;
if(vis[i.x] && d[i.x] < d[x]){
int t = (d[i.x] + d[x]) & 1;
if(!t) dc++;
S[t].upd(ps[i.x], -1);
S[t].upd(ps[x], 1);
}
else if(!vis[i.x]){
t[x].push_back(i.x);
d[i.x] = d[x] + 1;
g(i.x, i.i);
}
}
pe[x] = cnt;
}
void f(int x){
for(auto &i : t[x]){
f(i);
int t0 = S[0].get(ps[i], pe[i]);
int t1 = S[1].get(ps[i], pe[i]);
if(t0 == dc && !t1) ans++;
}
}
int main(){
scanf("%d%d", &n, &m);
for(int i = 0, x, y; i < m; i++){
scanf("%d%d", &x, &y);
e[x].push_back({y, i});
e[y].push_back({x, i});
}
for(int i = 1; i <= n; i++){
if(!vis[i]){
fl = 1;
col(i, 1);
if(!fl){
if(cr) T_T();
cr = i;
}
}
}
fill(vis + 1, vis + n + 1, 0);
if(!cr){
int rans = 0;
for(int i = 1; i <= n; i++){
if(vis[i]) continue;
ans = dc = 0;
g(i, -1);
if(dc > 1) ans = 0;
else if(dc == 1) ans = 1;
f(i);
rans += ans;
}
printf("%d\n", rans);
}
else{
g(cr, -1);
if(dc > 1) ans = 0;
else if(dc == 1) ans = 1;
f(cr);
printf("%d\n", ans);
}
}
