N, K = map(int, input().split())
X, Y = [0] * (N + 1), [0] * (N + 1)
for i in range(N):
    X[i + 1], Y[i + 1] = map(int, input().split())
    
N += 1
N2 = 1 << N
inf = 1e18
dp = [[[inf] * (K + 1) for _ in range(N)] for _ in range(N2)]
dp[1][0][K] = 0

def f(x1, y1, x2, y2):
    return ((x1 - x2) ** 2 + (y1 - y2) ** 2) ** 0.5

for s in range(N2):
    for i in range(N):
        if (s >> i) & 1 == 0:
            continue
        for k in range(K + 1):
            if dp[s][i][k] > inf/2:
                continue
            dp[s][0][K] = min(dp[s][0][K], dp[s][i][k] + f(X[0], Y[0], X[i], Y[i]))
            
    for i in range(N):
        if (s >> i) & 1 == 0:
            continue
        for k in range(K + 1):
            if dp[s][i][k] > inf/2:
                continue
            if k == 0:
                continue
            for j in range(N):
                if (s >> j) & 1:
                    continue
                ns = s | (1 << j)
                dp[ns][j][k - 1] = min(dp[ns][j][k - 1], dp[s][i][k] + f(X[i], Y[i], X[j], Y[j]))
         
print(dp[-1][0][K])