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


typedef unsigned long long int uint64;
typedef long long int          int64;
 
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define ABS(a) ((a)>(0)?(a):-(a))

void get_N (int64 *n)
{
  int cnt;
  
  cnt = scanf("%lld", n);

  return;
}

void get_NK (int64 *n, int64 *k)
{
  int cnt;
  
  cnt = scanf("%lld %lld", n, k);

  return;
}

void get_N1234 (int64 *n1, int64 *n2, int64 *n3, int64 *n4)
{
  int cnt;

  if (n2 == NULL) {
    cnt = scanf("%lld", n1);
    return;
  }
  if (n3 == NULL) {
    cnt = scanf("%lld %lld", n1, n2);
    return;
  }
  if (n4 == NULL) {
    cnt = scanf("%lld %lld %lld", n1, n2, n3);
    return;
  }
  cnt = scanf("%lld %lld %lld %lld", n1, n2, n3, n4);
  return;
}

void omit_LF (void)
{
  char c;
  int  cnt;
  
  cnt = scanf("%c", &c);
  return;
}

char *get_S (int64 n)
{
  char *buf;
  int  i;
  int  cnt;

  buf = (char *)malloc((size_t)(n * sizeof(char)));
  if (buf == NULL) {
    return NULL;
  }

  cnt = scanf("%s", buf);

  return buf;
}

char *get_SN (int64 max, int64 *size)
{
  char *buf;
  int  i;
  int  n;
  int  cnt;

  buf = (char *)malloc((size_t)(max * sizeof(char)));
  if (buf == NULL) {
    return NULL;
  }

  cnt = scanf("%s", buf);

  n = strlen(buf);

  *size = n;
  
  return buf;
}

int64 *get_NSeq (int64 n)
{
  int64 *buf;
  int64 i;

  buf = (int64 *)malloc((size_t)(n * sizeof(int64)));
  for (i=0; i<n; i++) {
    get_N(&buf[i]);
  }

  return buf;
}

typedef struct _tmp_t {
  int64    a;
  int64    b;
} tmp_t;

typedef int64 simple_t;

int compare_simple(const void *a, const void *b)
{
  simple_t *x;
  simple_t *y;

  x = (simple_t *)a;
  y = (simple_t *)b;

  if (x > y) return 1;
  if (y < x) return -1;

  return 0;
}
void qsort_simple (simple_t *array, int size)
{
  qsort(array, size, sizeof(simple_t), compare_simple);
}

int compare_a(const void *a, const void *b)
{
  tmp_t *x;
  tmp_t *y;

  x = (tmp_t *)a;
  y = (tmp_t *)b;

  if (x->a > y->a) return 1;
  if (x->a < y->a) return -1;

  return 0;
}

int compare_b(const void *a, const void *b)
{
  tmp_t *x;
  tmp_t *y;

  x = (tmp_t *)a;
  y = (tmp_t *)b;

  if (x->b > y->b) return 1;
  if (x->b < y->b) return -1;

  return 0;
}

void qsort_a (tmp_t *array, int size)
{
  qsort(array, size, sizeof(tmp_t), compare_a);
}

void qsort_b (tmp_t *array, int size)
{
  qsort(array, size, sizeof(tmp_t), compare_b);
}


int resolve1()
{
  int64 R;
  double pi=3.14159;
  double L;

  get_N(&R);

  L = pi*R*2;

  printf("%lf", L);
  return 0;
}

int resolve2()
{
  int64 N,M;
  int64 *A;
  int64 i;
  int64 total = 0;
  int64 play=0;
  
  get_NK(&N, &M);
  A = get_NSeq(M);

  for (i=0; i < M; i++) {
    total += A[i];
  }

  if (N >= total) {
    play = N - total;
  } else {
    printf("-1");
    return 0;
  }

  printf("%lld",play);
  return 0;
}


int main()
{
  int64 A,B,H,M;  //A: hour, B:min
  double wa, wb, wx;
  long double cc;
  double rad;

  get_N1234(&A,&B,&H,&M);

  wa = (360 / 12) * H;
  wa += ((360.0/12) / 60) * M;
  wb = (360 / 60) * M;

//  printf("wa=%f wb=%f\n", wa, wb); // for debug

  if (wa > wb) {
    if (wa - wb <= 180) {
      wx = wa - wb;
    } else {
      wx = 360 - (wa - wb);
    }
  } else {
    if (wb - wa <= 180) {
      wx = wb - wa;
    } else {
      wx = 360 - (wb - wa);
    }
  }

//  printf("wa=%f wb=%f wx=%f\n", wa, wb, wx); // for debug

#define PI 3.141592653589793

  rad = wx * PI / 180.0;
  
  cc = A*A + B*B - (2*A*B*cos(rad));

//  printf("%lf\n", cc); // for debug
  
  cc = sqrtl(cc);

  printf("%.10Lf", cc);

  return 0;
}



Measured memory_bytes: 2600