#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()
#define endl "\n"
#define rep(i, a, b) for (auto (i) = (a); (i) < (b); (i)++)
#define rrep(i, a, b) for (auto (i) = (a); (i) > (b); (i)--)

#define aim_cpo do{ios::sync_with_stdio(false);\
cin.tie(nullptr);cout.precision(12);cout<<fixed;}while(0)

#define LOCAL_INPUT do{FILE *stream1;\
stream1=freopen("/Users/aim_cpo/CLionProjects/competitive/in.txt","r",stdin);\
if(stream1==nullptr)return 0;}while(0)
#define LOCAL_OUTPUT do{FILE *stream2;\
stream2 = freopen("out.txt", "w", stdout);\
if (stream2 == nullptr) return 0;}while(0)

#ifdef LOCAL_DEFINE
#define show(x) cerr << #x << " = " << (x) << endl
#define dump(x) cerr << #x << " = " << (x) << " (line " << __LINE__ << ")" << endl
#define showV(v, n) do{\
for(int _i_t_e_=0; _i_t_e_<(n);_i_t_e_++)\
cerr<<"("<<_i_t_e_<<" = "<<(v)[_i_t_e_]<<") ";\
cerr<<endl;}while(0)
#define showA(a, n) do{\
for(int _i_t_e_=0;_i_t_e_<(n);_i_t_e_++)\
cerr<<"("<<_i_t_e_<<" = "<<(a)[_i_t_e_]<<") ";\
cerr<<endl;}while(0)
#define showA2(a, n, m) do{\
for(int _i_t_e_=0;_i_t_e_<(n);_i_t_e_++){\
for(int _i_t_e_2=0;_i_t_e_2<(m);_i_t_e_2++){\
cerr<<"("<<_i_t_e_<<", "<<_i_t_e_2<<" = "<<(a)[_i_t_e_][_i_t_e_2]<<") ";\
}cerr<<endl;}cerr<<endl;}while(0)
#else
#define show(x)
#define dump(x)
#define showV(v, n)
#define showA(a, n)
#define showA2(a, n, m)
#endif

typedef long long ll;
typedef unsigned long long ull;

constexpr const int INT_INF=0x3f3f3f3f; //1061109567
constexpr const ll LL_INF=0x3f3f3f3f3f3f3f3f; //4557430888798830399

template <typename T> bool chmin(T &a, T b){return a>b?(a=b,true):false;}
template <typename T> bool chmax(T &a, T b){return a<b?(a=b,true):false;}
template <typename T> void ln(T i, T n){cout<<(i==n-1?"\n":" ");}
template <typename T, typename S>
ostream &operator<<(ostream &out,const pair<T, S> &pair1){
  out<<'('<<pair1.fi<<", "<<pair1.se<<')';return out;}
template <typename T>
ostream &operator<<(ostream &out,const vector<T> &vector1){
  out<<'[';for(unsigned int i=0;i<vector1.size();i++){
    out<<vector1[i];if(i==vector1.size()-1)out<<"]";else out<<", ";
  }return out;
}

// INT
#define GCD(a, b) __gcd(a, b)
template <typename T> T LCM(T a, T b) {return a / GCD(a, b) * b;}
template <typename T> T EXTGCD(T a, T b, T& x, T& y) {
  T d = a;
  if (b != 0) {d=EXTGCD(b,a%b,y,x);y-=(a/b)*x;}
  else x=1,y=0;
  return d;
}
template <typename T> bool is_prime(T a) {
  for(int i=2;i*i<=a;i++)if(a%i==0)return 1;
  return 0;
}
template <typename T, typename S> T Pow(T a, S b) {
  T res = 1, now = a;
  while(b){if(b&1)res*=now;b>>=1;now*=now;}return res;
}

// MOD
ll MOD = 1000000000L + 7L;
#define add(a, b) ((a % MOD) + (b % MOD)) % MOD
#define mul(a, b) ((a % MOD) * (b % MOD)) % MOD
#define sub(a, b) ((a % MOD) + MOD - (b % MOD)) % MOD
template <typename T, typename S> T ModPow(T a, S b) {
  T res = 1, now = a;
  while(b){if(b&1)res=mul(res,now);b>>=1;now=mul(now,now);}return res;
}
template <typename T> T mod_inverse(T a, T mod, bool prime){ // if mod is prime, "prime" is true.
  if(prime)return ModPow(a, mod - 2);
  else{T x,y;EXTGCD(a,mod,x,y);return (mod+x%mod)%mod;}
}
#define divide(a, b) ((a % MOD) * (mod_inverse(b, MOD, true))) % MOD

//LLの数値をつかう時は最後にLをつける癖をつけよう
//
//  ┏┓┏┓　┓　┏┓
//  ┏┛┃┃　┃　┗┫
//  ┗┛┗┛　┻　┗┛
//
//   謹┃賀┃新┃年┃
//   ━┛━┛━┛━┛
//WWWWWWWWWWWWWWWWWWWWWW

template <typename T>
class BIT {
public:
    BIT(int size) {
      BITTable.assign(++size, 0);
    }
    T sum(int k) {
      T res = 0;
      for (++k; k > 0; k -= k & -k) {
        res += BITTable[k];
      }
      return res;
    }

    T sum(int l, int r) {
      if (l == 0) return sum(r);
      return sum(r) - sum(l - 1);
    }

    void update(int k, T x) { // b[k] += x;
      for (++k; k < (int)BITTable.size(); k += k & -k) BITTable[k] += x;
    }
private:
    vector <T> BITTable;
};

int n;
vector <pair <char, int> > v;
ll costB[2011][2011], costW[2011][2011];
ll dp[2011][2011];

int main() {
  aim_cpo; // インタラクティブのときは消すように.
#ifdef LOCAL_DEFINE
  LOCAL_INPUT; // インタラクティブのときは消すように.
//  LOCAL_OUTPUT; // ファイルに出力したいときのみ
  show(MOD);
#endif
  cin >> n;
  v.resize(2 * n);
  rep(i, 0, 2 * n) {
    cin >> v[i].fi >> v[i].se;
    v[i].se--;
  }
  rep(i, 0, n + 1) {
    BIT<ll> bit(n);
    ll white = 0;
    rep(j, 0, 2 * n) {
      if (v[j].fi == 'W') {
        if (v[j].se >= i) white++;
        continue;
      }
      costB[i][v[j].se] = bit.sum(v[j].se + 1, n - 1) + white;
      bit.update(v[j].se, 1);
    }
  }
  rep(i, 0, n + 1) {
    BIT<ll> bit(n);
    ll black = 0;
    rep(j, 0, 2 * n) {
      if (v[j].fi == 'B') {
        if (v[j].se >= i) black++;
        continue;
      }
      costW[i][v[j].se] = bit.sum(v[j].se + 1, n - 1) + black;
      bit.update(v[j].se, 1);
    }
  }
  showA2(costB, n, n);
  showA2(costW, n, n);
  rep(i, 0, 2001) rep(j, 0, 2001) dp[i][j] = LL_INF;
  dp[0][0] = 0;
  rep(i, 0, n + 1) {
    rep(j, 0, n + 1) {
      if (dp[i][j] == LL_INF) continue;
      if (i + 1 <= n) chmin(dp[i + 1][j], dp[i][j] + costW[j][i]);
      if (j + 1 <= n) chmin(dp[i][j + 1], dp[i][j] + costB[i][j]);
    }
  }
  cout << dp[n][n] << endl;
  showA2(dp, n + 1, n + 1);
#ifdef  LOCAL_DEFINE
  cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << "s." << endl;
#endif
  return 0;
}

Measured memory_bytes: 94976