func_code_string: #include <bits/stdc++.h>   using namespace std;   inline int read() {     int ret = 0, f = 1;     char ch = getchar();     while (ch >  9  || ch <  0 ) {       if (ch ==  - ) f = -1;       ch = getchar();     }     while (ch >=  0  && ch <=  9 ) {       ret = (ret << 1) + (ret << 3) + ch -  0 ;       ch = getchar();     }     return ret * f;   }   int n, m, x, y, deg[25];   bool edge[25][25], vis[25];   int main() {     n = read();     m = read();     for (register int i = 1; i <= m; i++) {       x = read();       y = read();       if (x == y) continue;       if (edge[x][y]) continue;       deg[x]++;       deg[y]++;       edge[x][y] = 1;       edge[y][x] = 1;     }     for (register int i = 1; i <= n; i++) {       int st = i, j;       memset(vis, 0, sizeof(vis));       vis[st] = 1;       for (j = 1; j < n; j++) {         int minn = 0, de = 0;         for (register int k = 1; k <= n; k++) {           if (edge[st][k] && !vis[k]) {             if (de == 0 || minn > deg[k]) {               de = k;               minn = deg[k];             }           }         }         if (de == 0) break;         st = de;         vis[st] = 1;       }       if (j == n) {         printf( Yes n );         return 0;       }     }     printf( No n );     return 0;   }   