s,a=801**.5-28,[0,0==0]
for i in range(int(input())):a+=[a[i]+a[-1]*int(1/s)];s=1/s-1//s
(print(a[-2]),) #.0fhlmop|
cyxhPTgwMSoqLjUtMjgsWzAsMD09MF0KZm9yIGkgaW4gcmFuZ2UoaW50KGlucHV0KCkpKTphKz1bYVtpXSthWy0xXSppbnQoMS9zKV07cz0xL3MtMS8vcwoocHJpbnQoYVstMl0pLCkgIy4wZmhsbW9wfA==