#include <bits/stdc++.h>
using namespace std;
int N, M, glob, sol;
struct EDGE
{
int u, v;
}E[200096];
bool flag;
int V[100096];
int DP[100096];
bool P[200096];
int PARENT[100096];
int UP[20][100096];
int SUM[2][200096];
vector <pair <int, int>> VG[100096];
inline void DFS(int node, vector <int> &I)
{
DP[node]++;
for(int i = 1; UP[i - 1][UP[i - 1][node]]; i++) UP[i][node] = UP[i - 1][UP[i - 1][node]];
for(pair <int, int> p : VG[node])
{
if(DP[p.second])
{
if(!P[p.first]) I.push_back(p.first);
P[p.first] = 1;
continue;
}
P[p.first] = 1;
V[p.second] = V[node] ^ 1;
DP[p.second] = DP[node];
UP[0][p.second] = node;
PARENT[p.second] = p.first;
DFS(p.second, I);
}
return;
}
inline int LCA(int u, int v)
{
if(DP[u] > DP[v]) swap(u, v);
for(int i = 16; i + 1; i--) if(DP[u] < DP[UP[i][v]]) v = UP[i][v];
if(DP[u] < DP[v]) v = UP[0][v];
if(u == v) return u;
for(int i = 16; i + 1; i--) if(UP[i][u] != UP[i][v]) u = UP[i][u], v = UP[i][v];
return UP[0][u];
}
inline pair <int, int> Pull(int node, vector <int> &I)
{
V[node] = 2;
pair <int, int> RET = {0, 0}, temp;
for(pair <int, int> p : VG[node])
{
if(V[p.second] == 2) continue;
I.push_back(p.first);
temp = Pull(p.second, I);
SUM[0][p.first] += temp.first;
SUM[1][p.first] += temp.second;
RET.first += SUM[0][p.first];
RET.second += SUM[1][p.first];
}
return RET;
}
inline void Solve(int node)
{
int RET = 0, counter[2] = {0, 0};
bool temp;
V[node] = 1;
vector <int> I;
DFS(node, I);
for(int x : I)
{
temp = V[E[x].u] ^ V[E[x].v];
counter[temp]++;
SUM[temp][PARENT[E[x].u]]++;
SUM[temp][PARENT[E[x].v]]++;
SUM[temp][PARENT[LCA(E[x].u, E[x].v)]] -= 2;
}
I.clear();
if(counter[0] && flag) {cout << "0\n"; exit(0);}
if(flag) return;
Pull(node, I);
for(int x : I) RET += (SUM[0][x] == counter[0]) && (!SUM[1][x]);
sol += counter[0] == 1;
sol += RET;
flag = bool(counter[0]);
return;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> N >> M;
int u, v;
for(int i = 1; i <= M; i++)
{
cin >> u >> v;
if(u > v) swap(u, v);
E[i] = {u, v};
VG[u].push_back({i, v});
VG[v].push_back({i, u});
}
for(int i = 1; i <= N; i++) if(!DP[i]) Solve(i);
while(!sol);
cout << sol << '\n';
return 0;
}
