def fib(n): if n <= 2: return ((n + 1) >> 1, (n + 2) >> 1) a, b = fib(n >> 1) if n & 1: return (a * a + b * b, b * ((a << 1) + b)) else: return (a * ((b << 1) - a), a * a + b * b) def fast_divmod(N, D, threshold=1<<512): i_prec = 50 if N < threshold or D < (1 << i_prec): return divmod(N, D) if N < D: return (0, N) guard_bits = 3 ilog2_n = N.bit_length() ilog2_d = D.bit_length() ilog2_q = ilog2_n + 1 - ilog2_d n_shamt = ilog2_n - (ilog2_q + guard_bits) d = D >> (ilog2_d - i_prec) reciprocal = int(float(1 << (2 * i_prec)) / float(d)) prec = ilog2_q precs = [] while prec > i_prec: precs.append(prec) prec = (prec >> 1) + guard_bits curr_prec = i_prec for prec in precs[::-1]: if prec >= ilog2_d: d = D lshift = prec - ilog2_d else: d = D >> (ilog2_d - prec) lshift = 0 r = (1 << prec) - (((d * reciprocal) << lshift) >> curr_prec) left = reciprocal << (prec - curr_prec) right = (reciprocal * r) >> curr_prec reciprocal = left + right curr_prec = prec n = N >> n_shamt q = (n * reciprocal) >> (curr_prec + guard_bits + 1) r = N - q * D if r < 0: while r < 0: r += D q -= 1 elif r >= D: while r >= D: r -= D q += 1 return q, r def print_big_integer(N, out, newline=True, beg=0, tens=None): def rec(N, e, zerofill=False): if e <= 10: if not zerofill: out.write("%s" % str(N)[beg:]) else: out.write("%0*d" % (1 << e, N)) else: ten = tens[e-1] q, r = fast_divmod(N, ten) if zerofill or q: rec(q, e - 1, zerofill) rec(r, e - 1, True) else: rec(r, e - 1, zerofill) if N < 0: N = -N out.write("-") if tens is None: tens = [] ten = 10 while ten <= N: tens.append(ten) if ten.bit_length() * 2 - 1 > N.bit_length(): break ten *= ten e = 0 while e < len(tens) and N >= tens[e]: e += 1 rec(N, e) if newline: print("") return def prob303(): import sys n = int(sys.stdin.readline()) if n == 2: print("3") print("INF") else: if n & 1: ans = fib(n)[0] else: a, b = fib(n // 2 - 1) ans = (a * b) << 1 print(n) # print(ans) print_big_integer(ans, sys.stdout) prob303()