#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define ll long long
const int N=1e5+50,lg=18;
vector<int>E[N];
vector<pair<int,int>>edges;
int n,m;
int par[N][lg+1],depth[N],in[N],out[N],tajm;
bool was[N];
void DFS(int u,int p=0){
in[u]=++tajm;was[u]=true;
par[u][0]=p;depth[u]=depth[p]+1;
for(int i=1;i<=lg;i++)par[u][i]=par[par[u][i-1]][i-1];
for(auto i:E[u]){
if(!was[i])DFS(i,u);
else if(i!=p)edges.pb({i,u});
}
out[u]=tajm;
}
int LCA(int u,int v){
if(depth[u]<depth[v])swap(u,v);
for(int i=lg;i>=0;i--)if(depth[par[u][i]]>=depth[v])u=par[u][i];if(u==v)return u;
for(int i=lg;i>=0;i--)if(par[u][i]!=par[v][i])u=par[u][i],v=par[v][i];return par[u][0];
}
int Dist(int u,int v){return depth[u]+depth[v]-2*depth[LCA(u,v)];}
int main(){
scanf("%i%i",&n,&m);
for(int i=1;i<=m;i++){
int u,v;scanf("%i%i",&u,&v);
E[u].pb(v);E[v].pb(u);
}
for(int i=1;i<=n;i++)if(!was[i])DFS(i);
int num=0,U=0,V=0;
for(auto [u,v]:edges){
int D=Dist(u,v);
//printf("%i %i: %i\n",u,v,D);
if(D%2==0){
num++;
if(num==1)U=u,V=v;
int c1=LCA(u,U),c2=LCA(u,V);
if(depth[c1]<depth[c2])swap(c1,c2);
int U1=c1,V1;
c1=LCA(v,U),c2=LCA(v,V);
if(depth[c1]<depth[c2])swap(c1,c2);
V1=c1;
if(depth[U1]<depth[LCA(u,v)]||depth[V1]<depth[LCA(u,v)])U1=V1=0;
U=U1,V=V1;
}
}
//for(int i=1;i<=n;i++)printf("%i -> %i\n",i,par[i][0]);
int res=0;
if(num==0){
}
else if(num==1) res=Dist(U,V)+1;
else res=Dist(U,V);
printf("%i\n",res);
return 0;
}
