void Solve(StreamScanner ss, StreamWriter sw)
{
//---------------------------------
var N = ss.Next(int.Parse);
var Balls = ss.Next(String, 2, 2 * N).Select(a => new { Color = a[0], Number = int.Parse(a[1]) }).ToArray();
//??????????????????
var bi = new int[N + 1];
var wi = new int[N + 1];
for (var i = 0; i < N * 2; i++)
{
var ball = Balls[i];
if (ball.Color == "B")
{
bi[ball.Number] = i;
}
if (ball.Color == "W")
{
wi[ball.Number] = i;
}
}
//Number???????Index??????????
var bs = new int[N + 1, N * 2]; //[Number, Index]
var ws = new int[N + 1, N * 2]; //[Number, Index]
for (var i = 1; i <= N; i++)
{
for (var j = 0; j < N * 2; j++)
{
bs[i, j] = bs[i - 1, j] + (j >= bi[i] ? 1 : 0);
}
for (var j = 0; j < N * 2; j++)
{
ws[i, j] = ws[i - 1, j] + (j >= wi[i] ? 1 : 0);
}
}
//B?i??W?j????????????????????????
var bc = new int[N, N + 1]; //[b, w]
var wc = new int[N + 1, N]; //[b, w]
for (var i = 0; i <= N; i++)
{
for (var j = 0; j <= N; j++)
{
if (i < N)
{
bc[i, j] = bi[i + 1] - bs[i, bi[i + 1]] - ws[j, bi[i + 1]];
}
if (j < N)
{
wc[i, j] = wi[j + 1] - bs[i, wi[j + 1]] - ws[j, wi[j + 1]];
}
}
}
//B?i??W?j?????????????
var dp = new long[N + 1, N + 1];//[b, w]
for (var i = 0; i <= N; i++)
{
for (var j = 0; j <= N; j++)
{
if (i == 0 && j == 0)
{
continue;
}
var b = i == 0 ? long.MaxValue : dp[i - 1, j] + bc[i - 1, j];
var w = j == 0 ? long.MaxValue : dp[i, j - 1] + wc[i, j - 1];
dp[i, j] = Math.Min(b, w);
}
}
sw.WriteLine(dp[N, N]);
//---------------------------------
}