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

    double min(double a,double b){
        if(a<b) return a;
        else return b;
    }
    int main(){
      double rad = 0.01745329252;
      int a,b,h,m;
      scanf("%d",&a);
      scanf("%d",&b);
      scanf("%d",&h);
      scanf("%d",&m);
      double angle = (h*30)+(m/2)-(m*6);
      angle = min(angle,360-angle);
      angle = angle*rad;
      double ca = cos(angle);
      double temp = 2*a*b*ca;
      double ans = sqrt((a*a)+(b*b)-temp);
      printf("%0.20f\n",ans);
      return 0;
    }
