#!/usr/bin/env python3.8
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


# %%
x, y = map(int, readline().split())
X = [x]
Y = [y]
W = [0]
N = int(readline())
for _ in range(N):
    x, y, w = readline().split()
    X.append(int(x))
    Y.append(int(y))
    W.append(float(w))

# %%
wt = [0] * (1 << N + 1)
for i, x in enumerate(W):
    for j in range(0, 1 << i):
        wt[j + (1 << i)] = wt[j] + x


# %%
INF = 10 ** 9
dp = [[INF] * (1 << N + 1) for _ in range(N + 1)]
dp[0][0] = 0
for n in range(1 << N + 1):
    for i in range(N + 1):
        if dp[i][n] == INF:
            continue
        for j in range(N + 1):
            if n & (1 << j):
                continue
            m = n ^ (1 << j)
            dist = abs(X[i] - X[j]) + abs(Y[i] - Y[j])
            cost = (wt[n] + 100) * dist
            x = dp[i][n] + cost
            if dp[j][m] > x:
                dp[j][m] = x


# %%
print(dp[0][-1] / 120 + sum(W))