Problem:
Score: 300 points

Problem Statement

Consider an analog clock whose hour and minute hands are A and B centimeters long, respectively.

An endpoint of the hour hand and an endpoint of the minute hand are fixed at the same point, around which each hand rotates clockwise at constant angular velocity. It takes the hour and minute hands 12 hours and 1 hour to make one full rotation, respectively.

At 0 o'clock, the two hands overlap each other. H hours and M minutes later, what is the distance in centimeters between the unfixed endpoints of the hands?

Constraints

All values in input are integers.

1 \leq A, B \leq 1000

0 \leq H \leq 11

0 \leq M \leq 59

Input

Input is given from Standard Input in the following format:

A B H M

Output

Print the answer without units. Your output will be accepted when its absolute or relative error from the correct value is at most 10^{-9}.

Sample Input 1

3 4 9 0

Sample Output 1

5.00000000000000000000

The two hands will be in the positions shown in the figure below, so the answer is 5 centimeters.

Sample Input 2

3 4 10 40

Sample Output 2

4.56425719433005567605

The two hands will be in the positions shown in the figure below. Note that each hand always rotates at constant angular velocity.

Solution in C (GCC 9.2.1) (judge verdict: Accepted)

/*
	ex3_2
	ruuu0048
*/
#include <stdio.h>
#include <math.h>
#define PI 3.14159265359 //πを定義
 
double radian_distance_cos(int hour,int minute); //時針と分針の間の角度の余弦を返す関数
 
int main(void){
 
 
    int hour_length,minute_length; //時針と分針の変数を宣言
    int hour,minute; //時間Hと分Mの変数を宣言
    double distance; //求める距離の変数を宣言
 
    scanf("%d %d %d %d",&hour_length,&minute_length,&hour,&minute); //それぞれ入力
    
    distance = sqrt(pow(hour_length,2) + pow(minute_length,2) - 2 * hour_length * minute_length * radian_distance_cos(hour,minute)); //余弦定理を使う
 
    printf("%.16f\n",distance); //答えを出力
 
    return 0; 
}
 
double radian_distance_cos(int hour,int minute){
 
    double hour_radian,minute_radian; //時針と分針の0時からの角度の変数を宣言
 
    hour_radian = ((double)hour + (double)minute / 60) / 12 * (2 * PI); //ラジアンに変換
 
    minute_radian = (double)minute / 60 * (2 * PI); //ラジアンに変換
 
    return cos(hour_radian - minute_radian); //差の予言を返す
 
};