#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

 
 
int main()
 {
	int a,b,h,m,e;
	double answer,t,k,c,d;
	
scanf("%d%d%d%d",&a,&b,&h,&m);


	c=30.0*h+m*0.50;
	d=6.0*m;

	k=c-d;

	if(k<0){
		k=-k;
	}

	if(k>180.0){
		k=k-180.0;
	}

t=k*(3.1415926535897932384626433832795028841971693/180.0);




	
	answer=sqrt(a*a+b*b-2.0*a*b*cos(t));




	printf("%.9f",answer);


	
			return 0;
	}


	





