void SolveSmall()
{
ans = 0;
var ids = new int[k];
double[,] dp = new double[20, 40];
for (int mask = 0; mask < 1 << n; ++mask)
{
if (BitUtils.CountOnes(mask) != k)
{
continue;
}
int z = 0;
for (int i = 0; i < n; i++)
{
if (BitUtils.BitInMask(mask, i))
{
ids[z++] = i;
}
}
dp[0, 0] = 1;
for (int i = 1; i <= k; i++)
{
for (int j = 0; j <= i; ++j)
{
dp[i, j] = p[ids[i - 1]] * (j == 0 ? 0 : dp[i - 1, j - 1]) + (1 - p[ids[i - 1]]) * dp[i - 1, j];
}
}
ans = Math.Max(ans, dp[k, k / 2]);
}
}