func_code_string: #include <bits/stdc++.h>   using namespace std;   const int Maxn = 507;   int n, m;   int E[Maxn][Maxn];   vector<int> V[Maxn];   int ans[Maxn];   bool mark[Maxn];   void dfs(int v) {     mark[v] = true;     for (int i = 0; i < V[v].size(); i++) {       int u = V[v][i];       if (!mark[u])         ans[u] = 2 - ans[v], dfs(u);       else if (ans[u] == ans[v]) {         cout <<  No  << endl;         exit(0);       }     }   }   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cin >> n >> m;     for (int i = 0; i < m; i++) {       int u, v;       cin >> u >> v;       E[u][v] = E[v][u] = 1;     }     for (int i = 1; i <= n; i++)       for (int j = 1; j <= n; j++)         if (!E[i][j] and i != j) V[i].push_back(j);     for (int i = 1; i <= n; i++) {       if (!V[i].size())         ans[i] = 1, mark[i] = true;       else if (!mark[i])         ans[i] = 2, dfs(i);     }     for (int i = 1; i <= n; i++)       for (int j = 1; j < i; j++) {         if (E[i][j] and abs(ans[i] - ans[j]) == 2) return cout <<  No  << endl, 0;       }     cout <<  Yes  << endl;     for (int i = 1; i <= n; i++) cout << (char)(ans[i] +  a );     cout << endl;   }   