arr = list(map(int, input().split()))

def minDist(x1,y1,x2,y2):
    return pow((pow((x1-x2),2)+pow((y1-y2),2)),0.5)

dist = minDist(arr[1],arr[2],arr[3],arr[4])

result= dist/(2*arr[0])
if result-int(result)==0:
    print(int(result))
else:
    print(int(result)+1)
