import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.io.UncheckedIOException;
import java.util.List;
import java.nio.charset.Charset;
import java.util.StringTokenizer;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author mikit
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        LightScanner in = new LightScanner(inputStream);
        LightWriter out = new LightWriter(outputStream);
        C3Steps solver = new C3Steps();
        solver.solve(1, in, out);
        out.close();
    }

    static class C3Steps {
        public void solve(int testNumber, LightScanner in, LightWriter out) {
            int n = in.ints(), m = in.ints();
            C3Steps.Node[] nodes = new C3Steps.Node[n];
            for (int i = 0; i < n; i++) {
                nodes[i] = new C3Steps.Node(i);
            }
            for (int i = 0; i < m; i++) {
                int a = in.ints() - 1, b = in.ints() - 1;
                nodes[a].adj.add(nodes[b]);
                nodes[b].adj.add(nodes[a]);
            }
            try {
                nodes[0].dfs(null, 0);
                long[] c = C3Steps.Node.cnt;
                out.ansln(c[0] * c[1] - m);
            } catch (RuntimeException ex) {
                out.ansln(n * (n - 1L) / 2 - m);
            }
        }

        private static class Node {
            private static long[] cnt = new long[2];
            int index;
            List<C3Steps.Node> adj = new ArrayList<>();
            int parity = -1;

            public Node(int index) {
                this.index = index;
            }

            private void dfs(C3Steps.Node from, int parity) {
                if (this.parity >= 0 && this.parity != parity) {
                    throw new RuntimeException();
                } else if (this.parity >= 0) {
                    return;
                }
                this.parity = parity;
                cnt[parity]++;
                for (C3Steps.Node node : adj) {
                    node.dfs(this, (parity + 1) % 2);
                }
            }

        }

    }

    static class LightScanner {
        private BufferedReader reader = null;
        private StringTokenizer tokenizer = null;

        public LightScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
        }

        public String string() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new UncheckedIOException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int ints() {
            return Integer.parseInt(string());
        }

    }

    static class LightWriter implements AutoCloseable {
        private final Writer out;
        private boolean autoflush = false;
        private boolean breaked = true;

        public LightWriter(Writer out) {
            this.out = out;
        }

        public LightWriter(OutputStream out) {
            this(new BufferedWriter(new OutputStreamWriter(out, Charset.defaultCharset())));
        }

        public LightWriter print(char c) {
            try {
                out.write(c);
                breaked = false;
            } catch (IOException ex) {
                throw new UncheckedIOException(ex);
            }
            return this;
        }

        public LightWriter print(String s) {
            try {
                out.write(s, 0, s.length());
                breaked = false;
            } catch (IOException ex) {
                throw new UncheckedIOException(ex);
            }
            return this;
        }

        public LightWriter ans(String s) {
            if (!breaked) {
                print(' ');
            }
            return print(s);
        }

        public LightWriter ans(long l) {
            return ans(Long.toString(l));
        }

        public LightWriter ansln(long... n) {
            for (long n1 : n) {
                ans(n1).ln();
            }
            return this;
        }

        public LightWriter ln() {
            print(System.lineSeparator());
            breaked = true;
            if (autoflush) {
                try {
                    out.flush();
                } catch (IOException ex) {
                    throw new UncheckedIOException(ex);
                }
            }
            return this;
        }

        public void close() {
            try {
                out.close();
            } catch (IOException ex) {
                throw new UncheckedIOException(ex);
            }
        }

    }
}



Measured memory_bytes: 56624