#include<stdio.h>
#include<algorithm>
#include<vector>
#include<stdlib.h>
using namespace std;
vector<int>con[100010];
int sw[100010],dap,n,m,x,y,ch[100010],anc[100010],arr[100010],w,top,lev[100010],check[100010],check2[100010];
struct data{
int x,y,z;
bool operator<(const data&r)const
{
return z<r.z;
}
}a[400010];
void dfs(int prev,int x,int p)
{
int i;
ch[x]=1; arr[++w]=x; lev[x]=p;
for(i=0;i<con[x].size();i++){
if(con[x][i]==prev && sw[x]==0){sw[x]=1; continue;}
if(ch[con[x][i]]){
if(lev[x]>=lev[con[x][i]]){top++; a[top].x=x; a[top].y=con[x][i];}
continue;
}
anc[con[x][i]]=x;
dfs(x,con[x][i],p+1);
}
}
void pro()
{
int i,s,p,sw=0,t=0,r,r2,cnt=0,cnt1=0,cnt2=0;
for(i=1;i<=top;i++) a[i].z=lev[a[i].y];
sort(a+1,a+top+1);
for(i=1;i<=top;i++){
s=lev[a[i].x]-lev[a[i].y];
if(s%2==1){
p=a[i].x; cnt1++;
while(check[p]==0){
if(p==a[i].y) break;
check[p]=1; cnt2++;
p=anc[p];
}
}
else if(!sw){
sw=1;
p=a[i].x; r=p; r2=a[i].y;
while(1){
if(p==a[i].y) break;
check2[p]=1;
p=anc[p];
}
}
}
if(sw==0)
{
dap+=w-1-cnt2;
return;
}
for(i=1;i<=top;i++)
{
s=lev[a[i].x]-lev[a[i].y];
if(s%2==0)
{
p=a[i].x;
while(check2[p]==0){
if(p==a[i].y || check2[p]==2 || check2[p]==3) break;
if(check2[p]==1){check2[p]=3; break;}
check2[p]=2;
p=anc[p];
}
}
}
cnt=0; p=0;
while(1)
{
if(r==r2) break;
if(check2[r]==3) p=cnt;
if(check[r]==0) cnt++;
r=anc[r];
}
if(dap && (cnt-p)){printf("0"); exit(0);}
if(dap && (top-cnt1)){printf("0"); exit(0);}
dap+=(cnt-p);
if(top-cnt1==1) dap++;
}
int main()
{
int i;
scanf("%d %d",&n,&m);
for(i=1;i<=m;i++){scanf("%d %d",&x,&y); con[x].push_back(y); con[y].push_back(x);}
for(i=1;i<=n;i++){
if(ch[i]==0)
{
dfs(0,i,1);
pro(); top=0; w=0;
}
}
printf("%d",dap);
return 0;
}
