import java.util.*;

public class Main {
    public static void main(String[] args ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int H = sc.nextInt();
        int M = sc.nextInt();

        //進度
        double tan = 0;
        tan = (H * 30) + (M * 0.5);
        double tyo = 0;
        tyo = (M * 6);

        // 角度
        double kaku = 0;
        kaku = (tan - tyo);

        // ラジアン
        double radi = Math.toRadians(kaku);
        
        // C
        double C = 0;
        C = Math.cos(radi);

        // 余弦定理
        C = Math.sqrt(((A*A) + (B*B)) - ((2*A*B)*C));
        System.out.println(C);

    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz