#include <bits/stdc++.h>
using namespace std;
void readi(int &x) {
  int v = 0, f = 1;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
void readll(long long &x) {
  long long v = 0ll, f = 1ll;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
void readc(char &x) {
  char c;
  while ((c = getchar()) == ' ')
    ;
  x = c;
}
void writes(string s) { puts(s.c_str()); }
void writeln() { writes(""); }
void writei(int x) {
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
void writell(long long x) {
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
inline long long inc(int &x) { return ++x; }
inline long long inc(long long &x) { return ++x; }
inline long long inc(int &x, long long y) { return x += y; }
inline long long inc(long long &x, long long y) { return x += y; }
inline double inc(double &x, double y) { return x += y; }
inline long long dec(int &x) { return --x; }
inline long long dec(long long &x) { return --x; }
inline long long dec(int &x, long long y) { return x -= y; }
inline long long dec(long long &x, long long y) { return x -= y; }
inline double dec(double &x, double y) { return x -= y; }
inline long long mul(int &x) { return x = ((long long)x) * x; }
inline long long mul(long long &x) { return x = x * x; }
inline long long mul(int &x, long long y) { return x *= y; }
inline long long mul(long long &x, long long y) { return x *= y; }
inline double mul(double &x, double y) { return x *= y; }
inline long long divi(int &x) { return x = sqrt(x); }
inline long long divi(long long &x) { return x = sqrt(x); }
inline long long divi(int &x, long long y) { return x /= y; }
inline long long divi(long long &x, long long y) { return x /= y; }
inline double divi(double &x, double y) { return x /= y; }
inline long long mod(int &x, long long y) { return x %= y; }
inline long long mod(long long &x, long long y) { return x %= y; }
int n, m, i, j, fa[1005], fa2[1005], y[100005], x[100005], cnt;
char c[100005];
set<int> used;
int find(int x) {
  if (fa[x] == x) return x;
  return fa[x] = find(fa[x]);
}
int find2(int x) {
  if (fa2[x] == x) return x;
  return fa2[x] = find2(fa2[x]);
}
int main() {
  ios_base::sync_with_stdio(false);
  ;
  cin >> n >> m;
  if (n % 2 == 0) {
    cout << -1;
    return 0;
  }
  if (1 <= (n))
    for (((i)) = (1); ((i)) <= ((n)); ((i))++) fa[i] = fa2[i] = i;
  if (1 <= (m))
    for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
      cin >> y[i] >> x[i] >> c[i];
      if (c[i] == 'S') {
        if (find(y[i]) != find(x[i])) {
          fa[find(y[i])] = find(x[i]);
        }
      }
    }
  if (1 <= (m))
    for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
      if (c[i] == 'M') {
        if (find(y[i]) != find(x[i])) {
          used.insert(i);
          fa[find(y[i])] = find(x[i]);
          if (find2(y[i]) != find2(x[i])) fa2[find2(y[i])] = find2(x[i]);
          cnt++;
          continue;
        }
      }
    }
  if (1 <= (m))
    for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
      if (cnt >= n / 2) break;
      if (c[i] == 'M' && !used.count(i)) {
        if (find2(y[i]) != find2(x[i])) {
          used.insert(i);
          if (find(y[i]) != find(x[i])) fa[find(y[i])] = find(x[i]);
          fa2[find2(y[i])] = find2(x[i]);
          cnt++;
          continue;
        }
      }
    }
  if (cnt != n / 2) {
    cout << -1;
    return 0;
  }
  if (1 <= (m))
    for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
      if (c[i] == 'S') {
        if (find2(y[i]) != find2(x[i])) {
          fa2[find2(y[i])] = find2(x[i]);
          used.insert(i);
        }
      }
    }
  if (used.size() != n - 1) {
    cout << -1;
    return 0;
  }
  cout << used.size() << endl;
  for (__typeof((used).begin()) it = (used).begin(); it != (used).end(); it++)
    cout << *it << ' ';
  return 0;
}
