#include <bits/stdc++.h>
using namespace std;
const int mxn = 1e3 + 5;
int Set(int N, int pos) { return N = N | (1 << pos); }
int reset(int N, int pos) { return N = N & ~(1 << pos); }
bool check(int N, int pos) { return (bool)(N & (1 << pos)); }
struct data {
  int U;
  int V;
  int idx;
};
vector<data> es, em;
vector<int> ans;
int par[mxn];
int unode[100005];
int vnode[100005];
int Find(int p) {
  if (p == par[p]) return p;
  return par[p] = Find(par[p]);
}
bool merge(int u, int v) {
  u = Find(u);
  v = Find(v);
  if (u == v) return false;
  par[v] = u;
  return true;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  for (int i = 0; i < mxn; i++) par[i] = i;
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int u, v;
    char c;
    cin >> u >> v >> c;
    unode[i] = u;
    vnode[i] = v;
    if (c == 'S')
      es.push_back({u, v, i});
    else {
      em.push_back({u, v, i});
      merge(u, v);
    }
  }
  if (!(n & 1)) {
    cout << -1 << '\n';
    return 0;
  }
  int cnt = 0;
  for (auto i : es) {
    if (merge(i.U, i.V)) {
      ans.push_back(i.idx);
      cnt++;
    }
  }
  for (int i = 0; i < mxn; i++) par[i] = i;
  for (auto i : ans) merge(unode[i], vnode[i]);
  int tt = (n - 1) >> 1;
  for (auto i : es) {
    if (cnt == tt) break;
    if (merge(i.U, i.V)) {
      ans.push_back(i.idx);
      cnt++;
    }
  }
  if (cnt != tt) {
    cout << -1 << '\n';
    return 0;
  }
  cnt = 0;
  for (auto i : em) {
    if (cnt == tt) break;
    if (merge(i.U, i.V)) {
      ans.push_back(i.idx);
      cnt++;
    }
  }
  if (cnt != tt) {
    cout << -1 << '\n';
    return 0;
  }
  cout << n - 1 << '\n';
  for (auto i : ans) cout << i + 1 << ' ';
  return 0;
}
