// G++ MACRO.CPP -STD=C++14
#include <bits/stdc++.h>
typedef long long ll;
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;
using namespace std;

#define dump(x)  cout << #x << " = " << (x) << endl;
#define YES(n) cout << ((n) ? "YES" : "NO"  ) << endl
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define POSSIBLE(n) cout << ((n) ? "POSSIBLE" : "IMPOSSIBLE"  ) << endl
#define Possible(n) cout << ((n) ? "Possible" : "Impossible"  ) << endl
#define possible(n) cout << ((n) ? "possible" : "impossible"  ) << endl

#define SANKOU(n,a,b) cout << ((n) ? (#a) : (#b) ) << endl

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define REPR(i,n) for(int i=n;i>=0;i--)

#define FOREACH(x,a) for(auto& (x) : (a) )

#define WFA(d,v) REP(k,v)REP(i,v)REP(j,v)d[i][j]=min(d[i][j],d[i][k]+d[k][j])

#define SCOUT(x) cout<<(x)<<" "
#define ENDL cout<<endl

#define VECCIN(x) for(auto&youso_: (x) )cin>>youso_
#define VECIN2(x,y) REP(i,x.size())cin>>x[i]>>y[i]
#define VECCOUT(x) if(1){for(auto tt=x.begin();tt!=x.end();tt++){if(tt!=x.begin())cout<<" ";cout<<(*tt);}cout<<endl;}

#define ALL(obj) (obj).begin(),(obj).end()

#define EXIST(n,x) (find(ALL(n),x)!=n.end())
#define UNIQUE(obj) sort(ALL( obj )); obj.erase(unique(ALL(obj)),obj.end())
#define EN(x) if(1){cout<<#x<<endl;return 0;}
#define COUT(x) cout<<(x)<<endl
void CINT(){}
template <class Head,class... Tail>
void CINT(Head&& head,Tail&&... tail){
    cin>>head;
    CINT(move(tail)...);
}
#define CIN(...) int __VA_ARGS__;CINT(__VA_ARGS__)
#define LCIN(...) ll __VA_ARGS__;CINT(__VA_ARGS__)
#define SCIN(...) string __VA_ARGS__;CINT(__VA_ARGS__)

template <class T = ll>
T IN(){T x;cin>>x;return (x);}

template <class Head>
void VT(Head head){}
template <class Head,class Seco,class... Tail>
void VT(Head&& head,Seco&& seco,Tail&&... tail){
    seco.resize(head);
    VT(head,move(tail)...);
}
void VT2(){}
template <class Head,class... Tail>
void VT2(Head&& head,Tail&&... tail){
  VECCIN(head);
  VT2(move(tail)...);
}

template <class Head>
void VT3(Head&& head){}
template <class Head,class Seco,class... Tail>
void VT3(Head&& head,Seco&& seco,Tail&&... tail){
  seco[head]=IN();
  VT3(head,move(tail)...);
}

#define VC1(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);VT2(__VA_ARGS__); //aaabbbccc
#define VC2(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);REP(i,n)VT3(i,__VA_ARGS__); //abcabcabc

// #include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision; // cpp_int

#define P pair<int,int>
#define V vector<int>
#define M map<int,int>
#define S set<int>

#define pb(a) push_back(a)
#define mp make_pair


int main(){
  //辺が三本もないなら 答えは0になる

  //二部グラフ3:3なら 片側からもう片側へ3本ずつ伸びていくので3*3=9本が限界
  //二部グラフ2:4なら 同じく2*4=8本が限界

  //二部グラフでないなら n*(n-1)/2 - m が答え

  CIN(n,m);VC2(m,a,b);REP(i,m){a[i]--;b[i]--;}
  if(m<3)EN(0);
  vector<V> edges(n);REP(i,m){edges[a[i]].pb(b[i]);edges[b[i]].pb(a[i]);}
  V color(n,0);
  color[0]=1;
  queue<int> que;que.push(0);
  auto f = [&]{
    while(!que.empty()){
      int t = que.front();que.pop();
      FOREACH(xx,edges[t]){
        if(color[xx]==color[t])
          return false;
        if(color[xx])continue;
        color[xx]=(color[t]==1?2:1);
        que.push(xx);
      }
    }
    return true;
  };

  if(f())
    COUT(1LL*count(ALL(color),1) * count(ALL(color),2) - m);
  else
    COUT(1LL*n*(n-1)/2 - m);

  return 0;
}


Measured memory_bytes: 7040