#include <bits/stdc++.h>
using namespace std;
const int maxn = 200005;
long long MOD = 1e9 + 7, INF = 1e18 + 1;
struct ed {
  int a, b;
  char c;
};
int n, m;
vector<int> par, size, necessary_s;
vector<ed> G;
int find_set(int v) {
  if (v == par[v]) return v;
  return par[v] = find_set(par[v]);
}
void make_set(int v) {
  par[v] = v;
  size[v] = 1;
}
void union_sets(int a, int b) {
  a = find_set(a);
  b = find_set(b);
  if (a != b) {
    if (size[a] < size[b]) swap(a, b);
    par[b] = a;
    size[a] += size[b];
  }
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  if (n % 2 == 0) return cout << -1, 0;
  par.resize(n + 1), size.resize(n + 1);
  G.resize(m + 1);
  for (int i = 1; i <= (int)(m); i++) cin >> G[i].a >> G[i].b >> G[i].c;
  for (int i = 1; i <= (int)(n); i++) make_set(i);
  for (int i = 1; i <= (int)(m); i++)
    if (G[i].c == 'M') union_sets(G[i].a, G[i].b);
  for (int i = 1; i <= (int)(m); i++)
    if (G[i].c == 'S' && find_set(G[i].a) != find_set(G[i].b)) {
      necessary_s.push_back(i);
      union_sets(G[i].a, G[i].b);
    }
  if ((int)(necessary_s).size() > (n - 1) / 2) return cout << -1, 0;
  int kks = 0;
  for (int i = 1; i <= (int)(n); i++)
    if (find_set(i) == i) kks++;
  if (kks > 1) return cout << -1, 0;
  for (int i = 1; i <= (int)(n); i++) make_set(i);
  for (int i = 0; i < (int)((int)(necessary_s).size()); i++) {
    int ted = necessary_s[i];
    union_sets(G[ted].a, G[ted].b);
  }
  int kuded = (int)(necessary_s).size();
  for (int i = 1; i <= (int)(m); i++)
    if (kuded < (n - 1) / 2 && G[i].c == 'S' &&
        find_set(G[i].a) != find_set(G[i].b)) {
      kuded++;
      union_sets(G[i].a, G[i].b);
      necessary_s.push_back(i);
    }
  if (kuded < (n - 1) / 2) return cout << -1, 0;
  for (int i = 1; i <= (int)(m); i++)
    if (G[i].c == 'M' && find_set(G[i].a) != find_set(G[i].b)) {
      union_sets(G[i].a, G[i].b);
      necessary_s.push_back(i);
    }
  cout << (int)(necessary_s).size() << endl;
  for (int i = 0; i < (int)((int)(necessary_s).size()); i++)
    cout << necessary_s[i] << ' ';
}
