func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   void maxtt(T& t1, T t2) {     t1 = max(t1, t2);   }   template <typename T>   void mintt(T& t1, T t2) {     t1 = min(t1, t2);   }   bool debug = 0;   int n, m, k;   string direc =  URDL ;   const long long MOD2 = (long long)1000000007 * (long long)1000000007;   long long ln, lk, lm;   void etp(bool f = 0) {     puts(f ?  YES  :  NO );     exit(0);   }   void addmod(int& x, int y, int mod = 1000000007) {     assert(y >= 0);     x += y;     if (x >= mod) x -= mod;     assert(x >= 0 && x < mod);   }   void et(int x = -1) {     printf( %d n , x);     exit(0);   }   long long fastPow(long long x, long long y, int mod = 1000000007) {     long long ans = 1;     while (y > 0) {       if (y & 1) ans = (x * ans) % mod;       x = x * x % mod;       y >>= 1;     }     return ans;   }   long long gcd1(long long x, long long y) { return y ? gcd1(y, x % y) : x; }   vector<int> mp[44];   int col[44];   int C, I;   bool bip = 1;   void dfs(int x, int color) {     col[x] = color;     for (int c : mp[x])       if (col[c] == 0)         dfs(c, 3 - color);       else if (col[c] != 3 - color)         bip = 0;   }   long long dp[(1 << 20) + 5], rdp[(1 << 20) + 5];   int to[44];   long long cal() {     if (n == 1) return 2;     int ln = n / 2, rn = n - ln;     for (int(i) = 0; (i) < (int)(1 << ln); (i)++) dp[i] = 1;     for (int(i) = 1; (i) <= (int)(ln); (i)++)       for (int j : mp[i])         if (j <= ln) {           dp[(1 << (i - 1)) | (1 << (j - 1))] = 0;         }     for (int s = 1; s < 1 << ln; s++) {       for (int(j) = 0; (j) < (int)(ln); (j)++)         if (s & (1 << j)) {           if (dp[s ^ (1 << j)] == 0) {             dp[s] = 0;             break;           }         }     }     int msk = (1 << ln) - 1;     for (int(i) = 0; (i) < (int)(1 << ln); (i)++) rdp[i] = dp[i ^ msk];     for (int j = 0; j < ln; j++) {       for (int i = msk; i >= 0; i--) {         if (~i & (1 << j)) {           rdp[i] += rdp[i ^ (1 << j)];         }       }     }     for (int(i) = 0; (i) < (int)(1 << rn); (i)++) dp[i] = 1;     for (int i = ln + 1; i <= n; i++)       for (int j : mp[i])         if (j > ln) {           dp[(1 << (i - ln - 1)) | (1 << (j - ln - 1))] = 0;         } else {           to[i - ln - 1] |= 1 << (j - 1);         }     for (int s = 1; s < 1 << rn; s++) {       for (int(j) = 0; (j) < (int)(rn); (j)++)         if (s & (1 << j)) {           if (dp[s ^ (1 << j)] == 0) {             dp[s] = 0;             break;           }         }     }     long long ans = 0;     for (int(i) = 0; (i) < (int)(1 << rn); (i)++)       if (dp[i]) {         int s = 0;         for (int(j) = 0; (j) < (int)(rn); (j)++)           if (i & (1 << j)) s |= to[j];         ans += rdp[s];       }     return ans;   }   void fmain(int tid) {     scanf( %d%d , &n, &m);     for (int i = 0, u, v; i < m; i++) {       scanf( %d%d , &u, &v);       mp[u].push_back(v);       mp[v].push_back(u);     };     for (int(i) = 1; (i) <= (int)(n); (i)++)       if (col[i] == 0) {         dfs(i, 1);         C++;       }     for (int(i) = 1; (i) <= (int)(n); (i)++)       if (mp[i].empty()) I++;     long long all = 1LL << n;     all -= 1LL << C;     all += 1LL << I;     if (bip) all += 1LL << C;     all += 1LL << I;     all -= m == 0 ? 1LL << n : 0;     all -= cal() * 2;     printf( %lld n , all);   }   int main() {     int t = 1;     for (int(i) = 1; (i) <= (int)(t); (i)++) {       fmain(i);     }     return 0;   }   