local F = require 'ffi'
local M = F.load 'ssl'
F.cdef [[
typedef struct bignum_st { uint64_t *d; int top; int dmax; int neg; int flag; } BN;
BN * BN_new(void);
void BN_free(BN *);
int BN_set_word(BN *, uint64_t);
int BN_mul_word(BN *, uint64_t);
char * BN_bn2dec(const BN *);
void CRYPTO_free(void *, const char *, int);
]]

print((function (f, g, n)
	if n>=50 then return "000000000000" end
	return f(g(n)):sub(-12)
end)(function (bn)
	return F.string(F.gc(M.BN_bn2dec(bn), function (a) M.CRYPTO_free(a,"",0) end))
end, function (n)
	local bn = F.gc(M.BN_new(), M.BN_free)
	M.BN_set_word(bn, 1)
	for i=2,n do M.BN_mul_word(bn, i) end
	return bn
end, io.stdin:read("*n")))