Problem: There are n blocks arranged in a row and numbered from left to right, starting from one. Each block is either black or white. 

You may perform the following operation zero or more times: choose two adjacent blocks and invert their colors (white block becomes black, and vice versa). 

You want to find a sequence of operations, such that they make all the blocks having the same color. You don't have to minimize the number of operations, but it should not exceed 3 ⋅ n. If it is impossible to find such a sequence of operations, you need to report it.

Input

The first line contains one integer n (2 ≤ n ≤ 200) — the number of blocks.

The second line contains one string s consisting of n characters, each character is either "W" or "B". If the i-th character is "W", then the i-th block is white. If the i-th character is "B", then the i-th block is black. 

Output

If it is impossible to make all the blocks having the same color, print -1.

Otherwise, print an integer k (0 ≤ k ≤ 3 ⋅ n) — the number of operations. Then print k integers p_1, p_2, ..., p_k (1 ≤ p_j ≤ n - 1), where p_j is the position of the left block in the pair of blocks that should be affected by the j-th operation.

If there are multiple answers, print any of them.

Examples

Input


8
BWWWWWWB


Output


3
6 2 4


Input


4
BWBB


Output


-1


Input


5
WWWWW


Output


0


Input


3
BWB


Output


2
2 1 

Note

In the first example, it is possible to make all blocks black in 3 operations. Start with changing blocks 6 and 7, so the sequence is "BWWWWBBB". Then change blocks 2 and 3, so the sequence is "BBBWWBB". And finally, change blocks 4 and 5, so all blocks are black.

It is impossible to make all colors equal in the second example.

All blocks are already white in the third example.

In the fourth example it is possible to make all blocks white in two operations: first operation is to change blocks 2 and 3 (so the sequence is "BBW"), and then change blocks 1 and 2 (so all blocks are white).

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
int debug = 1;
int test = 1;
long double pi = 3.14159265358979323846;
inline long long int min2(long long a, long long b) {
  if (a < b) {
    return a;
  }
  return b;
}
inline long long max3(long long a, long long b, long long c) {
  return (a) > (b) ? ((a) > (c) ? (a) : (c)) : ((b) > (c) ? (b) : (c));
}
inline long long min3(long long a, long long b, long long c) {
  return (a) < (b) ? ((a) < (c) ? (a) : (c)) : ((b) < (c) ? (b) : (c));
}
long long extgcd(long long a, long long b, long long &x, long long &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  long long d = extgcd(b, a % b, y, x);
  y -= a / b * x;
  return d;
}
inline long long mod(long long a, long long m) { return (a % m + m) % m; }
long long modinv(long long a) {
  long long x, y;
  extgcd(a, 1000000007, x, y);
  return mod(x, 1000000007);
}
long long gcd(long long u, long long v) {
  long long r;
  while (0 != v) {
    r = u % v;
    u = v;
    v = r;
  }
  return u;
}
long long lcm(long long u, long long v) { return u / gcd(u, v) * v; }
void get_all_factors(int a[], long long int n) {
  long long int w = sqrt(n);
  for (int i = 1; i <= w; i++) {
    if (n % i == 0) {
      a[i]++;
      a[n / i]++;
    }
  }
  long long int x = ceil(sqrt(n));
  if (sqrt(n) == ceil(sqrt(n))) a[(int)sqrt(n)]--;
}
long long int memo[100000][110] = {0};
long long C(long long n, long long r) {
  if (r == 0 || r == n) return 1;
  if (memo[n][r] != -1) return memo[n][r];
  return memo[n][r] =
             (C(n - 1, r - 1) % 1000000007 + C(n - 1, r) % 1000000007) %
             1000000007;
}
int valid(string s, int i) {
  if (s == "lol" or i == -1000050000) {
    return 0;
  }
  return 1;
}
void status(string s1 = "lol", long long int i1 = -1000050000,
            string s2 = "lol", long long int i2 = -1000050000,
            string s3 = "lol", long long int i3 = -1000050000) {
  if (debug) {
    if (valid(s1, i1)) {
      cout << s1 << "=" << i1 << "  ";
    }
    if (valid(s2, i2)) {
      cout << s2 << "=" << i2 << "  ";
    }
    if (valid(s3, i3)) {
      cout << s3 << "=" << i3 << "  ";
    }
    cout << endl;
  }
}
long long int poww(long long x, long long y) {
  long long res = 1;
  while (y) {
    if (y & 1) res = res * x;
    y = y >> 1;
    x = x * x;
  }
  return res;
}
long long int powm(long long x, long long y, long long m = 1000000007) {
  x = x % m;
  long long res = 1;
  while (y) {
    if (y & 1) res = res * x;
    res %= m;
    y = y >> 1;
    x = x * x;
    x %= m;
  }
  return res % m;
}
vector<vector<long long int> > multiply(vector<vector<long long int> > &a,
                                        vector<vector<long long int> > &b) {
  vector<vector<long long int> > c(a.size(),
                                   vector<long long int>(b[0].size()));
  assert(a[0].size() == b.size());
  long long int mod = 1000000007;
  for (int i = 0; i < a.size(); i++) {
    for (int j = 0; j < b[0].size(); j++) {
      c[i][j] = 0;
      for (int k = 0; k < a[0].size(); k++) {
        c[i][j] += (a[i][k] * b[k][j]) % mod;
        c[i][j] %= mod;
      }
    }
  }
  return c;
}
vector<vector<long long int> > fastmatrix(vector<vector<long long int> > &a,
                                          long long int n) {
  if (n == 1) {
    return a;
  }
  if (n == 0) {
    vector<vector<long long int> > k = a;
    for (int i = 0; i < a.size(); i++) {
      for (int j = 0; j < a[i].size(); j++) {
        k[i][j] = 1;
      }
    }
    return k;
  }
  if (n % 2 == 1) {
    vector<vector<long long int> > k = fastmatrix(a, n / 2);
    vector<vector<long long int> > kk = multiply(k, k);
    kk = multiply(kk, a);
    return kk;
  } else {
    vector<vector<long long int> > k = fastmatrix(a, n / 2);
    vector<vector<long long int> > kk = multiply(k, k);
    return kk;
  }
}
vector<long long int> prime(10000000, 1);
void sieve() {
  for (int i = 2; i <= 10000; i++) {
    if (prime[i]) {
      for (int j = i * i; j < 10000000; j += i) {
        prime[j] = 0;
      }
    }
  }
}
class comp {
 public:
  bool operator()(pair<long long int, pair<long long int, long long int> > &a,
                  pair<long long int, pair<long long int, long long int> > &b) {
    if (a.first == b.first) {
      return a.second.first > b.second.first;
    }
    return a.first < b.first;
  }
};
long long int getsum(long long int x) { return (x * (x + 1)) / 2; }
void filereader() {}
int comp(int a, int b) { return a > b; }
int main() {
  filereader();
  debug = 0;
  test = 0;
  int tt = 1;
  if (test) {
    cin >> tt;
  }
  while (tt--) {
    int n;
    cin >> n;
    string second;
    cin >> second;
    int bcnt = 0, wcnt = 0;
    vector<pair<long long int, pair<long long int, long long int> > > pre;
    int i = 0;
    while (1) {
      int s, e;
      s = i;
      int f = 0;
      while (i < n and second[i] == 'B') {
        bcnt++;
        i++;
      }
      e = i - 1;
      if (e >= s) {
        f = 1;
        pre.push_back(make_pair('B', make_pair(s, e)));
      }
      s = i;
      while (i < n and second[i] == 'W') {
        wcnt++;
        i++;
      }
      e = i - 1;
      if (e - s >= 0) {
        f = 1;
        pre.push_back(make_pair('W', make_pair(s, e)));
      }
      if (i == n) {
        break;
      }
    }
    if (pre.size() == 1) {
      cout << 0 << endl;
      return 0;
    }
    vector<long long int> moves;
    int rem = 0;
    if (bcnt % 2 == 0) {
      for (int i = 0; i < pre.size(); i++) {
        if (pre[i].first == 'B') {
          int s = pre[i].second.first;
          int e = pre[i].second.second;
          int cnt = e - s + 1;
          int j = s;
          if (rem == 2) {
            j++;
          }
          while (j <= e) {
            moves.push_back(j);
            j += 2;
          }
          if (rem == 2) {
            if (cnt % 2 == 0) {
              rem = 1;
            } else {
              rem = 0;
            }
          } else {
            rem = cnt % 2;
          }
        } else {
          if (rem > 0) {
            rem++;
            int s = pre[i].second.first;
            int e = pre[i].second.second;
            int cnt = e - s + 1;
            int j = s;
            while (j <= e) {
              moves.push_back(j);
              j += 1;
            }
          }
        }
      }
    } else if (wcnt % 2 == 0) {
      for (int i = 0; i < pre.size(); i++) {
        if (pre[i].first == 'W') {
          int s = pre[i].second.first;
          int e = pre[i].second.second;
          int cnt = e - s + 1;
          int j = s;
          if (rem == 2) {
            j++;
          }
          while (j <= e) {
            moves.push_back(j);
            j += 2;
          }
          if (rem == 2) {
            if (cnt % 2 == 0) {
              rem = 1;
            } else {
              rem = 0;
            }
          } else {
            rem = cnt % 2;
          }
        } else {
          if (rem > 0) {
            rem++;
            int s = pre[i].second.first;
            int e = pre[i].second.second;
            int cnt = e - s + 1;
            int j = s;
            while (j <= e) {
              moves.push_back(j);
              j += 1;
            }
          }
        }
      }
    } else {
      cout << -1 << endl;
      return 0;
    }
    cout << moves.size() << endl;
    for (auto i : moves) {
      cout << i + 1 << " ";
    }
  }
}