#pragma GCC optimize("O3")

#include <iostream>
#include <cstring>
#include <string>
#include <cassert>
#include <random>
#include <cmath>
#include <algorithm>
#include <map>
#include <unordered_map>
#include <queue>
#include <set>

namespace fastinput {
	/** Interface */

	template <class T = int> inline T readInt();
	inline long double readDouble();
	inline int readUInt();
	inline int readChar();
	inline void readWord(char *s);
	inline bool readLine(char *s); // do not save '\n'
	inline bool isEof();
	inline int peekChar();
	inline bool seekEof();

	template <class T> inline void writeInt(T x, int len = -1);
	template <class T> inline void writeUInt(T x, int len = -1);
	inline void writeChar(int x);
	inline void writeWord(const char *s);
	inline void writeDouble(long double x, int len = 0);
	inline void flush();

	/** Read */

	static const int buf_size = 4096;

	static char buf[buf_size];
	static int buf_len = 0, buf_pos = 0;

	inline bool isEof() {
		if (buf_pos == buf_len) {
			buf_pos = 0, buf_len = fread(buf, 1, buf_size, stdin);
			if (buf_pos == buf_len)
				return 1;
		}
		return 0;
	}

	inline int getChar() {
		return isEof() ? -1 : buf[buf_pos++];
	}

	inline int peekChar() {
		return isEof() ? -1 : buf[buf_pos];
	}

	inline bool seekEof() {
		int c;
		while ((c = peekChar()) != -1 && c <= 32)
			buf_pos++;
		return c == -1;
	}

	inline int readChar() {
		int c = getChar();
		while (c != -1 && c <= 32)
			c = getChar();
		return c;
	}

	inline int readUInt() {
		int c = readChar(), x = 0;
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		return x;
	}

	template <class T>
	inline T readInt() {
		int s = 1, c = readChar();
		T x = 0;
		if (c == '-')
			s = -1, c = getChar();
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		return s == 1 ? x : -x;
	}

	inline long double readDouble() {
		int s = 1, c = readChar();
		long double x = 0;
		if (c == '-')
			s = -1, c = getChar();
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		if (c == '.') {
			c = getChar();
			long double coef = 1;
			while ('0' <= c && c <= '9')
				x += (c - '0') * (coef *= 0.1), c = getChar();
		}
		return s == 1 ? x : -x;
	}

	inline void readWord(char *s) {
		int c = readChar();
		while (c > 32)
			*s++ = (char)c, c = getChar();
		*s = 0;
	}

	inline bool readLine(char *s) {
		int c = getChar();
		while (c != '\n' && c != -1)
			*s++ = (char)c, c = getChar();
		*s = 0;
		return c != -1;
	}

	/** Write */

	static int write_buf_pos = 0;
	static char write_buf[buf_size];

	inline void writeChar(int x) {
		if (write_buf_pos == buf_size)
			fwrite(write_buf, 1, buf_size, stdout), write_buf_pos = 0;
		write_buf[write_buf_pos++] = (char)x;
	}

	inline void flush() {
		if (write_buf_pos)
			fwrite(write_buf, 1, write_buf_pos, stdout), write_buf_pos = 0;
	}

	template <class T>
	inline void writeInt(T x, int output_len) {
		if (x < 0)
			writeChar('-'), x = -x;

		char s[24];
		int n = 0;
		while (x || !n)
			s[n++] = '0' + x % 10, x /= 10;
		while (n < output_len)
			s[n++] = '0';
		while (n--)
			writeChar(s[n]);
	}

	template <class T>
	inline void writeUInt(T x, int output_len) {
		char s[24];
		int n = 0;
		while (x || !n)
			s[n++] = (char)('0' + (char)(x % 10)), x /= 10;
		while (n < output_len)
			s[n++] = '0';
		while (n--)
			writeChar(s[n]);
	}

	inline void writeWord(const char *s) {
		while (*s)
			writeChar(*s++);
	}

	inline void writeDouble(long double x, int output_len) {
		if (x < 0)
			writeChar('-'), x = -x;
		int t = (int)x;
		writeUInt(t), x -= t;
		writeChar('.');
		for (int i = output_len - 1; i > 0; i--) {
			x *= 10;
			t = std::min(9, (int)x);
			writeChar('0' + t), x -= t;
		}
		x *= 10;
		t = std::min(9, (int)(x + 0.5));
		writeChar('0' + t);
	}
}

using namespace fastinput;
using namespace std;

/** Begin fast allocation */
const int MAX_MEM = 2e8;
int mpos = 0;
char mem[MAX_MEM];
inline void * operator new (size_t n) {
	mpos += n;
	return (void *)(mem + mpos - n);
}
inline void operator delete (void *) noexcept {} // must have!
												 /** End fast allocation */

const int N = 1e5;
vector <int> g[N];
bool used[N];
int color[N];
bool conflict = false;

void dfs(int i, int clr = 0) {
	if (used[i])
		return;
	used[i] = 1;
	color[i] = clr;
	clr ^= 1;
	for (auto x : g[i]) {
		if (used[x]) {
			if (color[x] != clr)
				conflict = true;
		} else {
			dfs(x, clr);
		}
	}
}

int main() {
	int n = readInt(), m = readInt();
	for (int i = 0; i < m; ++i) {
		int a = readInt(), b = readInt();
		--a, --b;
		g[a].push_back(b);
		g[b].push_back(a);
	}
	dfs(0);
	if (conflict) {
		cout << (1LL * n * (n - 1) / 2) - m << endl;
	} else {
		long long cnt[2] = {0, 0};
		for (int i = 0; i < n; ++i) {
			++cnt[color[i]];
		}
		cout << cnt[0] * cnt[1] - m << endl;
	}
	
	return 0;
}

Measured memory_bytes: 6912