#include<stdio.h>
#include<cmath>

int main(){
double x1,x2,y1,y2,r,R;
scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);
r=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
R=sqrt(r);
printf("%lf\n",R);
return 0;
}
### Prompt

Your challenge is to write a cpp solution to the following problem:

Write a program which calculates the distance between two points P1(x1, y1) and P2(x2, y2).



Input

Four real numbers x1, y1, x2 and y2 are given in a line.

Output

Print the distance in real number. The output should not contain an absolute error greater than 10-4.

Example

Input

0 0 1 1


Output

1.41421356

### Response

```cpp
#include<stdio.h>
#include<cmath>

int main(){
double x1,x2,y1,y2,r,R;
scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);
r=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
R=sqrt(r);
printf("%lf\n",R);
return 0;
}
```