#include <bits/stdc++.h>

#define HEAP priority_queue
#define rep(i, n) for(int i = 0, _end_ = (n); i < _end_; ++i)
#define per(i, n) for(int i = (n) - 1; i >= 0 ; --i)
#define forn(i, l, r) for(int i = (l), _end_ = (r); i <= _end_; ++i)
#define nrof(i, r, l) for(int i = (r), _end_ = (l); i >= _end_; --i)
#define FOR(a, b) for(auto (a): (b))
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define X first
#define Y second
#define eps 1e-6
#define pi 3.1415926535897932384626433832795
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(), x.end()

using namespace std;

typedef long long LL;
typedef double flt;
typedef vector<int> vi;
typedef vector<LL> vl;
typedef pair<int,int> pii;
typedef pair<int,LL> pil;
typedef pair<LL,int> pli;
typedef pair<LL,LL> pll;
typedef vector<pil> vil;
typedef vector<pii> vii;
typedef vector<pli> vli;
typedef vector<pll> vll;

const int iinf = 1e9 + 7;
const int oo = 0x3f3f3f3f;
const LL linf = 1ll << 60;
const flt dinf = 1e60;

template <typename T> inline void scf(T &x)
{
    bool f = 0;
    x = 0;
    char c = getchar();
    while(c != '-' && (c < '0' || c > '9')) c = getchar();
    if(c == '-') f = 1, c = getchar();
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    if(f) x = -x;
    return;
}

template <typename T1, typename T2> void scf(T1 &x, T2 &y)
{
    scf(x);
    return scf(y);
}

template <typename T1, typename T2, typename T3> void scf(T1 &x, T2 &y, T3 &z)
{
    scf(x);
    scf(y);
    return scf(z);
}

template <typename T1, typename T2, typename T3, typename T4> void scf(T1 &x, T2 &y, T3 &z, T4 &w)
{
    scf(x);
    scf(y);
    scf(z);
    return scf(w);
}

inline char mygetchar()
{
    char c = getchar();
    while(c == ' ' || c == '\n') c = getchar();
    return c;
}

template <typename T> inline bool chkmax(T &x, const T &y)
{
    return y > x ? x = y, 1 : 0;
}

template <typename T> inline bool chkmin(T &x, const T &y)
{
    return y < x ? x = y, 1 : 0;
}

#ifdef DEBUG
#define debug(...) fprintf(stderr, __VA_ARGS__)
#else
#define debug(...)
#endif

//---------------------------------------------------------head----------------------------------------------------

const int maxn = 1e5 + 100;

int n, m;
vi g[maxn];
int col[maxn], dep[maxn];

void dfs(int u, int c) {
    if(col[u]) {
        return;
    }
    col[u] = c;
    for (int v: g[u]) {
        dfs(v, -c);
    }
    return;
}

void dfs2(int u, int p = 0) {
    for(int v: g[u]) {
        if(v != p) {
            dep[v] = dep[u] + 1;
            dfs2(v, u);
        }
    }
    return;
}

int main()
{
    scf(n, m);
    rep(i, m) {
        int u, v;
        scf(u, v);
        g[u].pb(v);
        g[v].pb(u);
    }
    dfs(1, -1);
    bool f = 0;
    forn(u, 1, n) {
        for (int v: g[u]) {
            if(col[u] == col[v]) {
                f = 1;
                break;
            }
        }
        if(f) {
            break;
        }
    }
    if(f) {
        printf("%lld\n", 1ll * n * (n - 1) / 2 - m);
        return 0;
    }
    if(m == n - 1) {
        forn(u, 1, n) {
            if(SZ(g[u]) == 1) {
                dfs2(u);
                f = 0;
                forn(v, 1, n) {
                    if(dep[v] > 2) {
                        f = 1;
                        break;
                    }
                }
                if(!f) {
                    printf("%d\n", m - m);
                    return 0;
                }
                break;
            }
        }
    }
    int x = 0, y = 0;
    forn(u, 1, n) {
        if(col[u] == -1) {
            ++x;
        }
        else ++y;
    }
    printf("%lld\n", 1ll * x * y - m);
    return 0;
}


Measured memory_bytes: 6528