inp = raw_input().split()
r = int(inp[0])
x = int(inp[1])
y = int(inp[2])
X = int(inp[3])
Y = int(inp[4])
#tan = (Y-y)/(X-x)
dist = ((X-x)**2+(Y-y)**2)
dist = dist**(0.5)
step = 0
#print dist,r
inc = r*2
inc /= 2**0.5
step=(dist/inc)
if(step*inc!=dist):
    step+=1
print int(step)
