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