
from math import ceil

def main():
    
    r, x1, y1, x2, y2 = map(float, input().split())
    
    x = ((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))**(.5)
    print(ceil(x/(2*r)))

if __name__ == '__main__':
    main()