import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
double x1 = sc.nextDouble(), y1 = sc.nextDouble();
double x2 = sc.nextDouble(), y2 = sc.nextDouble();
double dx = x1 - x2;
double dy = y1 - y2;
double dist = Math.sqrt(dx * dx + dy * dy);
System.out.printf("%.4f", dist);
}
}
````
----------
### 算法1
##### (暴力枚举) $O(n^2)$
blablabla
#### 时间复杂度
#### 参考文献
#### C++ 代码
blablabla
----------
### 算法2
##### (暴力枚举) $O(n^2)$
blablabla
#### 时间复杂度
#### 参考文献
#### C++ 代码
blablabla
```