/*  This Code is Submitted by wywcgs for Problem 2016 on 2005-09-18 at 11:15:54 */ 
#include <stdio.h>
#include <math.h>
#define  PI  3.1415926535897

int main()
{
    double r, h, d1, d2, A1, A2;
    double l, dis, p, A;
    
    while(scanf("%lf %lf %lf %lf %lf %lf", &r, &h, &d1, &A1, &d2, &A2) == 6) {
        l = sqrt(r * r + h * h);
        A = fabs(A2 - A1);
        if(A - 180 > 1e-3) {
            A = (double)360 - A;
        }    
        p = PI * A * r / (l * 180);
        dis = sqrt(d1*d1 + d2*d2 - 2*d1*d2*cos(p));
        printf("%.2lf\n", dis);
    }
    
    return 0;
}