10868: ABC157 - F - Yakiniku Optimization Problem
[Creator : ]
Description
Takahashi wants to grill $N$ pieces of meat on a grilling net, which can be seen as a two-dimensional plane. The coordinates of the $i$-th piece of meat are $\left(x_i, y_i\right)$, and its hardness is $c_i$.
Takahashi can use one heat source to grill the meat. If he puts the heat source at coordinates $\left(X, Y\right)$, where $X$ and $Y$ are real numbers, the $i$\-th piece of meat will be ready to eat in $c_i \times \sqrt{\left(X - x_i\right)^2 + \left(Y-y_i\right)^2}$ seconds.
Takahashi wants to eat $K$ pieces of meat. Find the time required to have $K$ or more pieces of meat ready if he put the heat source to minimize this time.
Takahashi can use one heat source to grill the meat. If he puts the heat source at coordinates $\left(X, Y\right)$, where $X$ and $Y$ are real numbers, the $i$\-th piece of meat will be ready to eat in $c_i \times \sqrt{\left(X - x_i\right)^2 + \left(Y-y_i\right)^2}$ seconds.
Takahashi wants to eat $K$ pieces of meat. Find the time required to have $K$ or more pieces of meat ready if he put the heat source to minimize this time.
Input
Input is given from Standard Input in the following format:
```
$N$ $K$
$x_1$ $y_1$ $c_1$
$\vdots$
$x_N$ $y_N$ $c_N$
```
```
$N$ $K$
$x_1$ $y_1$ $c_1$
$\vdots$
$x_N$ $y_N$ $c_N$
```
Output
Print the answer.
It will be considered correct if its absolute or relative error from our answer is at most $10^{-6}$.
It will be considered correct if its absolute or relative error from our answer is at most $10^{-6}$.
Constraints
- All values in input are integers.
- $1 \leq N \leq 60$
- $1 \leq K \leq N$
- $-1000 \leq x_i , y_i \leq 1000$
- $\left(x_i, y_i\right) \neq \left(x_j, y_j\right) \left(i \neq j \right)$
- $1 \leq c_i \leq 100$
- $1 \leq N \leq 60$
- $1 \leq K \leq N$
- $-1000 \leq x_i , y_i \leq 1000$
- $\left(x_i, y_i\right) \neq \left(x_j, y_j\right) \left(i \neq j \right)$
- $1 \leq c_i \leq 100$
Sample 1 Input
4 3
-1 0 3
0 0 3
1 0 2
1 1 40
Sample 1 Output
2.4
If we put the heat source at $\left(-0.2, 0\right)$, the $1$-st, $2$-nd, and $3$-rd pieces of meat will be ready to eat within $2.4$ seconds. This is the optimal place to put the heat source.
Sample 2 Input
10 5
-879 981 26
890 -406 81
512 859 97
362 -955 25
128 553 17
-885 763 2
449 310 57
-656 -204 11
-270 76 40
184 170 16
Sample 2 Output
7411.2252