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;
const long double PI = 3.1415926535897932384626433832795;
const long double EPS = 1e-11;
int n, m, u, v, start;
vector<int> g[1000100];
signed long long step[1000100];
signed long long kd;
set<pair<int, int> > st;
set<pair<int, int> > stin;
bool used[1000100];
void dfs(int V) {
  used[V] = 1;
  for (int i = 0; i < (g[V].size()); i++) {
    if (g[V][i] == V) st.insert(make_pair(V, V));
    pair<int, int> p = make_pair(V, g[V][i]);
    if (p.first > p.second) swap(p.first, p.second);
    st.insert(p);
    if (!used[g[V][i]]) dfs(g[V][i]);
  }
}
int main() {
  cin >> n >> m;
  for (int i = 0; i < (m); i++) {
    cin >> u >> v;
    u--, v--;
    start = u;
    if (u == v) kd++;
    g[u].push_back(v);
    g[v].push_back(u);
    pair<int, int> p = make_pair(u, v);
    if (p.first > p.second) swap(p.first, p.second);
    stin.insert(p);
    if (u != v) {
      step[u]++;
      step[v]++;
    }
  }
  dfs(start);
  if (stin.size() != st.size()) {
    cout << -10 << endl;
    return 0;
  }
  signed long long ans = 0;
  for (int i = 0; i < (n); i++) ans += step[i] * (step[i] - 1) / 2;
  cout << ans + kd * (m - 1) - kd * kd << endl;
  return 0;
}
