100 10
87 73
15 71
14 33
1 4
20 80
65 67
36 36
25 4
22 21
7 97
 4 2
3 3
3 4
 5 4
3 3
4 4
5 5
1 2
 4 4
1 2
2 3
3 1
4 4
 4 3
1 1
2 3
3 4
 1000000 1
255765 255765
 4 3
1 2
2 3
4 4
 4 2
1 1
1 2
 3 3
1 1
2 2
3 3
 5 4
1 1
2 3
2 4
2 5
 4 5
1 4
3 4
1 2
2 3
2 4
 4 4
2 3
2 4
3 4
4 4
 10 9
8 10
3 10
2 8
9 3
4 8
1 10
7 9
5 4
7 3
 10 10
1 2
2 3
3 4
4 5
5 1
6 6
7 7
8 8
9 9
10 10
 5 5
1 4
3 4
1 2
2 3
2 4
 3 3
1 2
2 2
3 3
 5 3
1 1
2 2
3 3
 6 12
1 2
1 3
2 3
1 1
2 2
3 3
4 5
5 6
4 6
4 4
5 5
6 6
 4 4
1 2
2 3
1 3
4 4
 5 4
1 2
3 3
4 4
5 5
 7 13
6 7
2 7
3 7
4 3
5 2
1 4
7 7
3 1
5 5
3 3
1 5
2 6
6 6
 2 2
1 1
2 2
 5 5
1 1
2 2
3 3
4 4
5 5
 1 1
1 1
 7 3
1 1
3 3
6 6
 3 3
1 1
2 3
3 3

0 1 0 0 0 0 0 1 0 0 8 6 12 0 8 0 0 0 0 0 57 0 0 0 0 0
#include <bits/stdc++.h>
using namespace std;
typedef pair<long long, long long> ll;
typedef vector<long long> vl;
typedef vector<ll> vll;
vl a[200000];
vl ans(200000, -1);
long long bfs(long long node) {
  queue<long long> q;
  q.push(node);
  ans[node] = 0;
  while (!q.empty()) {
    node = q.front();
    q.pop();
    for (long long i = (0); i < (a[node].size()); i++) {
      if (ans[a[node][i]] == -1) {
        ans[a[node][i]] = ans[node] + 1;
        q.push(a[node][i]);
      }
    }
  }
  return *max_element((ans).begin(), (ans).end());
}
int main() {
  long long n, m;
  cin >> n >> m;
  for (long long i = (0); i < (m); i++) {
    long long x, y;
    cin >> x >> y;
    x--;
    y--;
    a[x].push_back(y);
    a[y].push_back(x);
  }
  long long x = bfs(0);
  for (long long i = (0); i < (n); i++)
    if (a[i].size() > 0 and ans[i] == -1) {
      cout << "0";
      return 0;
    }
  long long res = 0;
  long long node;
  for (long long i = (0); i < (n); i++)
    if (ans[i] == x) {
      res++;
      node = i;
    }
  fill((ans).begin(), (ans).end(), -1);
  x = bfs(node);
  res = 0;
  for (long long i = (0); i < (n); i++)
    if (ans[i] == x) {
      res++;
    }
  cout << (res * (res - 1)) / 2 + res;
  return 0;
}
