#include <bits/stdc++.h>   using namespace std;   inline void splay(int &v) {     v = 0;     char c = 0;     int p = 1;     while (c <  0  || c >  9 ) {       if (c ==  - ) p = -1;       c = getchar();     }     while (c >=  0  && c <=  9 ) {       v = (v << 3) + (v << 1) + c -  0 ;       c = getchar();     }     v *= p;   }   struct Edge {     int to, next;     int col;   } edge[200010];   int first[100010], size;   void addedge(int x, int y, int z) {     size++;     edge[size].to = y;     edge[size].next = first[x];     first[x] = size;     edge[size].col = z;   }   int n, m, tmp;   bool f, flag;   int cnt = 100001, ans[100010], p[100010];   int C[100010];   bool vis[100010];   int ff[100010], sum;   void dfs(int now, int col) {     ff[++sum] = now;     vis[now] = 1;     C[now] = col;     if (C[now]) tmp++;     for (int u = first[now]; u; u = edge[u].next) {       if (vis[edge[u].to]) {         if (edge[u].col) {           if (C[edge[u].to] == C[now]) f = 0;         } else {           if (C[edge[u].to] != C[now]) f = 0;         }       } else {         dfs(edge[u].to, col ^ edge[u].col);       }     }   }   void get() {     f = 1;     int _cnt = 0;     memset(vis, 0, sizeof vis);     for (int i = 1; i <= n; i++) {       if (!vis[i]) {         sum = 0;         tmp = 0;         dfs(i, 0);         if (f && tmp <= sum - tmp) {           for (int i = 1; i <= sum; i++) {             if (C[ff[i]]) {               p[++_cnt] = ff[i];             }           }         }         if (f && sum - tmp < tmp) {           for (int i = 1; i <= sum; i++) {             if (!C[ff[i]]) {               p[++_cnt] = ff[i];             }           }         }       }     }     if (f) {       if (_cnt <= cnt) {         for (int i = 1; i <= _cnt; i++) {           ans[i] = p[i];         }         cnt = _cnt;         flag = true;       }     }   }   int main() {     splay(n), splay(m);     for (int i = 1; i <= m; i++) {       int x, y, z;       char op[5];       splay(x), splay(y), scanf( %s , op);       if (op[0] ==  B )         z = 0;       else         z = 1;       addedge(x, y, z), addedge(y, x, z);     }     get();     for (int i = 1; i <= size; i++) {       edge[i].col ^= 1;     }     get();     if (flag) {       printf( %d n , cnt);       for (int i = 1; i <= cnt; i++) {         printf( %d  , ans[i]);       }     } else       puts( -1 );   }   