import math
r, x, y , x2, y2 = input().split()
r = int(r)
x = int(x)
y = int(y)
x2 = int(x2)
y2 = int(y2)

dist = math.sqrt(pow((x - x2), 2) + pow((y - y2), 2));

resp = dist / (2 * r);

if (resp * r * 2) < dist:
    resposta +=1
    
resp = int(resp)

print(resp)
  	  	 		  			 		   	 	   			 	