from math import sqrt
s = input().split()
s = [int(s) for s in s]
r,x,y,x1,y1 = s[0],s[1],s[2],s[3],s[4]
d = sqrt((x-x1)**2+(y-y1)**2)
ans = d // (r*2)
if d > ans*r*2:
    ans += 1
print(int(ans))

        
    
