#include <bits/stdc++.h>
using namespace std;

// Define
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template <class T> using pvector = vector<pair<T, T>>;
template <class T>
using rpriority_queue = priority_queue<T, vector<T>, greater<T>>;
using graph = vector<vector<ll>>;
template <class T> using wgraph = vector<vector<ll, T>>;
constexpr const ll dx[4] = {1, 0, -1, 0};
constexpr const ll dy[4] = {0, 1, 0, -1};
constexpr const ll MOD = 1e9 + 7;
constexpr const ll mod = 998244353;
constexpr const ll INF = 1LL << 60;
constexpr const ll inf = 1 << 30;
constexpr const char rt = '\n';
constexpr const char sp = ' ';
#define rt(i, n) (i == (ll)(n) -1 ? rt : sp)
#define len(x) ((ll)(x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define ifn(x) if (not(x))
#define elif else if
#define elifn else ifn
#define fi first
#define se second

template <class T> bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T> bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}

// Debug
#define debug(...)                                                             \
    {                                                                          \
        cerr << __LINE__ << ": " << #__VA_ARGS__ << " = ";                     \
        for (auto &&X : {__VA_ARGS__}) cerr << "[" << X << "] ";               \
        cerr << rt;                                                            \
    }

#define dump(a, h, w)                                                          \
    {                                                                          \
        cerr << __LINE__ << ": " << #a << " = [" << rt;                        \
        rep(_i, h) {                                                           \
            rep(_j, w) {                                                       \
                if (abs(a[_i][_j]) >= INF / 2 and a[_i][_j] <= -INF / 2)       \
                    cerr << '-';                                               \
                if (abs(a[_i][_j]) >= INF / 2)                                 \
                    cerr << "∞" << sp;                                         \
                else                                                           \
                    cerr << a[_i][_j] << sp;                                   \
            }                                                                  \
            cerr << rt;                                                        \
        }                                                                      \
        cerr << "]" << rt;                                                     \
    }

#define vdump(a, n)                                                            \
    {                                                                          \
        cerr << __LINE__ << ": " << #a << " = [";                              \
        rep(_i, n) {                                                           \
            if (_i) cerr << sp;                                                \
            if (abs(a[_i]) >= INF / 2 and a[_i] <= -INF / 2) cerr << '-';      \
            if (abs(a[_i]) >= INF / 2)                                         \
                cerr << "∞" << sp;                                             \
            else                                                               \
                cerr << a[_i];                                                 \
        }                                                                      \
        cerr << "]" << rt;                                                     \
    }

// Loop
#define inc(i, a, n) for (ll i = (a), _##i = (n); i <= _##i; ++i)
#define dec(i, a, n) for (ll i = (a), _##i = (n); i >= _##i; --i)
#define rep(i, n) for (ll i = 0, _##i = (n); i < _##i; ++i)
#define each(i, a) for (auto &&i : a)

// Stream
#define fout(n) cout << fixed << setprecision(n)
struct io {
    io() { cin.tie(nullptr), ios::sync_with_stdio(false); }
} io;

// Speed
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

// Math
inline constexpr ll gcd(const ll a, const ll b) {
    return b ? gcd(b, a % b) : a;
}
inline constexpr ll lcm(const ll a, const ll b) { return a / gcd(a, b) * b; }

inline constexpr ll modulo(const ll n, const ll m = MOD) {
    ll k = n % m;
    return k + m * (k < 0);
}
inline constexpr ll chmod(ll &n, const ll m = MOD) {
    n %= m;
    return n += m * (n < 0);
}
inline constexpr ll mpow(ll a, ll n, const ll m = MOD) {
    ll r = 1;
    rep(i, 64) {
        if (n & (1LL << i)) r *= a;
        chmod(r, m);
        a *= a;
        chmod(a, m);
    }
    return r;
}
inline ll inv(const ll n, const ll m = MOD) {
    ll a = n, b = m, x = 1, y = 0;
    while (b) {
        ll t = a / b;
        a -= t * b;
        swap(a, b);
        x -= t * y;
        swap(x, y);
    }
    return modulo(x, m);
}

struct UFS {
    vector<ll> data;
    UFS(ll N) : data(N, -1) {}
    ll root(ll x) {
        if (data[x] < 0)
            return x;
        else
            return data[x] = root(data[x]);
    }
    bool unite(ll x, ll y) {
        ll root_x = root(x), root_y = root(y);
        if (root_x != root_y) {
            if (data[root_x] > data[root_y]) swap(root_x, root_y);
            data[root_x] += data[root_y];
            data[root_y] = root_x;
            return true;
        }
        return false;
    }
    bool same(ll x, ll y) { return root(x) == root(y); }
    bool isroot(ll x) { return x == root(x); }
    ll size(ll x) { return -data[root(x)]; }
    ll size() {
        ll cnt = 0;
        rep(i, data.size()) if (isroot(i)) cnt++;
        return cnt;
    }
};

using unionfind = UFS;
ll isBipartite(graph &G) {
    unionfind UF(2 * len(G));
    rep(i, len(G)) each(j, G[i]) {
        UF.unite(i, len(G) + j);
        UF.unite(j, len(G) + i);
    }
    if (UF.same(0, len(G))) {
        return 0;
    } else {
        ll cnt = 0;
        rep(i, len(G)) if (UF.same(0, i)) cnt++;
        return cnt;
    }
}

istream &operator>>(istream &is, graph &g) {
    ll a, b;
    is >> a >> b;
    g[a - 1].pb(b - 1);
    g[b - 1].pb(a - 1);
    return is;
}

template <class T> istream &operator>>(istream &is, wgraph<T> &g) {
    ll a, b;
    T c;
    is >> a >> b >> c;
    g[a - 1].pb({b - 1, c});
    g[b - 1].pb({a - 1, c});
    return is;
}

signed main() {
    ll N, M;
    cin >> N >> M;
    graph G(N);
    rep(i, M) cin >> G;
    ll num = isBipartite(G);
    debug(num);
    if (num) {
        cout << num * (N - num) - M << rt;
    } else {
        cout << N * (N - 1) / 2 - M << rt;
    }
}

Measured memory_bytes: 10852