#pragma comment(linker, "/stack:200000000") #pragma GCC optimize("Ofast") #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") // need #include #include // data structure #include #include #include #include #include #include #include #include #include //#include #include #include #include #include // stream //#include #include //#include #include // etc #include #include #include #include #include #include #include // input #define INIT std::ios::sync_with_stdio(false);std::cin.tie(0); #define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__); template void MACRO_VAR_Scan(T& t) { std::cin >> t; } templatevoid MACRO_VAR_Scan(First& first, Rest& ...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); } #define VEC_ROW(type, n, ...)std::vector __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int w_=0; w_ void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); } templatevoid MACRO_VEC_ROW_Init(int n, First& first, Rest& ...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); } template void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; } templatevoid MACRO_VEC_ROW_Scan(int p, First& first, Rest& ...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); } #define VEC(type, c, n) std::vector c(n);for(auto& i:c)std::cin>>i; #define MAT(type, c, m, n) std::vector> c(m, std::vector(n));for(auto& R:c)for(auto& w:R)std::cin>>w; // output #define OUT(dist) std::cout<<(dist); #define FOUT(n, dist) std::cout<=(a);--w) #define REP(w, n) for(int w=0;w=0;--w) #define IN(a, x, b) (a<=x && x inline T CHMAX(T & a, const T b) { return a = (a < b) ? b : a; } template inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; } #define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]" #define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;} //void CHECKTIME(std::function f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast((end - start)).count(); std::cerr << "[Time:" << res << "ns (" << res / (1.0e9) << "s)]\n"; } // test template using V = std::vector; template using VV = V>; template std::ostream& operator<<(std::ostream& os, std::pair p) { os << "(" << p.first << ", " << p.second << ")"; return os; } #define random_shuffle "USE std::shuffle!"; // type/const #define int ll using ll = long long; using ull = unsigned long long; using ld = long double; using PAIR = std::pair; using PAIRLL = std::pair; constexpr int INFINT = (1 << 30) - 1; // 1.07x10^ 9 constexpr int INFINT_LIM = (1LL << 31) - 1; // 2.15x10^ 9 constexpr ll INFLL = 1LL << 60; // 1.15x10^18 constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62); // 9.22x10^18 constexpr double EPS = 1e-10; constexpr int MOD = 1000000007; constexpr double PI = 3.141592653589793238462643383279; template void FILL(T(&a)[N], const T & val) { for (auto& x : a) x = val; } template void FILL(ARY(&a)[N][M], const T & val) { for (auto& b : a) FILL(b, val); } template void FILL(std::vector & a, const T & val) { for (auto& x : a) x = val; } template void FILL(std::vector> & a, const T & val) { for (auto& b : a) FILL(b, val); } // ------------>8------------------------------------->8------------ std::vector Eratosthenes(int n) { std::vector num(n, true); std::vector prime; num[0] = false; for (int i = 0; i * i < n; ++i) { if (num[i]) { for (int j = 2; (i + 1) * j <= n; ++j) { num[(i + 1) * j - 1] = false; } } } for (int i = 0; i < n; ++i) { if (num[i]) { prime.push_back(i + 1); } } return prime; } std::vector> primeFact(ll n) { std::vector> result; for (ll i = 2; i * i <= n; ++i) { int divCount = 0; if (n % i == 0) { do { ++divCount; n /= i; } while (n % i == 0); result.emplace_back(i, divCount); } } if (n != 1) result.emplace_back(n, 1); return result; } signed main() { INIT; VAR(int, n, p); if (p == 1) { OUT(1)BR; return 0; } auto pv(primeFact(p)); auto ev(Eratosthenes(n)); if (pv.size() == 1) { if (pv[0].first * 2 > n) { OUT(1)BR; return 0; } } int ans = n - 1; for (auto& prime : ev) { if (prime * 2 > n) --ans; } OUT(ans)BR; return 0; }