#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; typedef long long ll; typedef vector vl; typedef vector> vvl; typedef pair P; #define rep(i, n) for(ll i = 0; i < n; i++) #define exrep(i, a, b) for(ll i = a; i <= b; i++) #define out(x) cout << x << endl #define exout(x) printf("%.10f\n", x) #define chmax(x, y) x = max(x, y) #define chmin(x, y) x = min(x, y) #define all(a) a.begin(), a.end() #define rall(a) a.rbegin(), a.rend() #define pb push_back #define re0 return 0 const ll mod = 998244353; const ll INF = 1e16; struct Eratosthenes { vl isprime; // isprime[i] : iが素数なら1 vl minfactor; // minfactor[i] : iを割り切る最小の素数 vl mobius; // mobius[i] : メビウス関数 μ(i) Eratosthenes(ll n) : isprime(n+1, 1), minfactor(n+1, -1), mobius(n+1, 1) { isprime[1] = 0; minfactor[1] = 1; exrep(p, 2, n) { if(!isprime[p]) { continue; } minfactor[p] = p; mobius[p] = -1; for(ll q = 2*p; q <= n; q += p) { isprime[q] = 0; if(minfactor[q] == -1) { minfactor[q] = p; } if((q / p) % p == 0) { mobius[q] = 0; } else { mobius[q] = -mobius[q]; } } } } // 高速素因数分解。O(log(n))でnを素因数分解する vector

factorize(ll n) { // (素因数, 指数) のvectorを返す vector

res; while(n > 1) { ll p = minfactor[n]; ll i = 0; while(minfactor[n] == p) { n /= p; i++; } res.emplace_back(make_pair(p, i)); } return res; } // 高速約数列挙。O(σ(n))でnの約数を求める。σ(n)はnの約数の個数 vl divisors(ll n) { vl res({1}); auto pf = factorize(n); for(auto p : pf) { ll s = res.size(); rep(i, s) { ll x = 1; rep(j, p.second) { x *= p.first; res.pb(res[i] * x); } } } return res; } }; int main() { ll n; double p; cin >> n >> p; Eratosthenes e(n+1); double ans = 0.0; exrep(i, 2, n) { vl v = e.divisors(i); int m = v.size() - 2; if(m == 0) { ans += 1.0; } else { ans += pow(1.0 - p, m); } } exout(ans); re0; }