#include <bits/stdc++.h>

using namespace std;

#define Rabbir_Reaper ios::sync_with_stdio(0);cin.tie();

#define N 100005

vector<int> adj[N];

int visit[N];

int black,white,tblack,twhite;

void dfs(int pos){

    if(visit[pos]==1) tblack++;

    if(visit[pos]==2) twhite++;

    for(auto &u:adj[pos]){

        if(visit[u]==0){

            visit[u]=3-visit[pos];

            dfs(u);

        }else if(visit[u] != 3-visit[pos]){

            tblack=-1;

            twhite=0;

            break;

        }

    }

}

int main(){

    Rabbir_Reaper

    int n,m;

    cin>>n>>m;

    for(int i=0,u,v;i<m;i++){

        cin>>u>>v;

        adj[u].push_back(v);

        adj[v].push_back(u);

    }

    for(int i=0;i<n;i++){

        if(visit[i]==0){

            visit[i]=1;

            dfs(i);

            black+=min(tblack,twhite);

            white+=max(tblack,twhite);

            if(tblack == -1){

                black=0;

                break;

            }

            tblack=0;

            twhite=0;

        }

    }

    cout<<black;

}