#include int main() { using namespace std; unsigned long M, N; cin >> M >> N; unsigned long value{1}, ord_2{}, ord_5{}; if(N > M - N)N = M - N; const auto multiplies{[&value, &ord_2, &ord_5](unsigned long x){ while(x && x % 2 == 0){ ++ord_2; x /= 2; } while(x && x % 5 == 0){ ++ord_5; x /= 5; } (value *= x) %= 100000000; }}; const auto divides{[&value, &ord_2, &ord_5](unsigned long x){ while(x && x % 2 == 0){ --ord_2; x /= 2; } while(x && x % 5 == 0){ --ord_5; x /= 5; } (value *= [](unsigned long a, unsigned long n){ unsigned long r{1}; while(n){ if(n & 1)(r *= a) %= 100000000; (a *= a) %= 100000000; n /= 2; } return r; }(x, 4999999)) %= 100000000; }}; for(unsigned long i{}; i < N; ++i){ multiplies(M - i); divides(i + 1); } ord_2 = min(ord_2, 10UL); ord_5 = min(ord_5, 10UL); assert(ord_2 < M && ord_5 < M); while(ord_2 > 0){ --ord_2; (value *= 2) %= 100000000; } while(ord_5 > 0){ --ord_5; (value *= 5) %= 100000000; } printf("%08lu\n", value); return 0; }