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- #include <bits/stdc++.h>
- using namespace std;
- vector<pair<int, int>> cant;
- /*int comb(int n, int k) {
- string b(k, 1);
- b.resize(n, 0);
- int ans = 0;
- do {
- set<int> d;
- for(int i = 0; i < n; i++) {
- if(b[i]) {
- d.insert(i + 1);
- }
- }
- for(auto k : cant) {
- if(d.count(k.first) != 0 and d.count(k.second) != 0) {
- ans++;
- break;
- }
- }
- } while(prev_permutation(b.begin(), b.end()));
- return ans;
- }*/
- int main() {
- ios_base::sync_with_stdio(false);
- cin.tie(0);
- int n, m;
- cin >> n >> m;
- for(int i = 0; i < m; i++) {
- int a, b;
- cin >> a >> b;
- cant.push_back({a, b});
- }
- if(m == 0) {
- cout << (1 << n) - 1 << "\n";
- return 0;
- }
- int ans = (1 << n) - 1;
- /*ans -= cant.size();
- for(int i = 3; i <= n; i++) {
- ans -= comb(n, i);
- }*/
- for(int i = 0; i < (1 << n); i++) {
- set<int> d;
- int t = 1;
- int p = i;
- while(i > 0) {
- if(i & 1) {
- d.insert(t);
- }
- t++;
- i >>= 1;
- }
- i = p;
- for(auto k : cant) {
- if(d.count(k.first) != 0 and d.count(k.second) != 0) {
- ans--;
- break;
- }
- }
- }
- cout << ans << "\n";
- return 0;
- }
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