#include #include #include #include #include #include #include #include using namespace std; #define int long long #define FOR(i, a, b) for(int i=(a);i<(b);i++) #define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--) #define REP(i, n) for(int i=0; i<(n); i++) #define RREP(i, n) for(int i=(n-1); i>=0; i--) #define ALL(a) (a).begin(),(a).end() #define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end()); #define CONTAIN(a, b) find(ALL(a), (b)) != (a).end() #define array2(type, x, y) array, x> #define vector2(type) vector > #define out(...) printf(__VA_ARGS__) typedef pair pos; int pos::*x = &pos::first; int pos::*y = &pos::second; int dxy[] = {0, 1, 0, -1, 0}; /*================================*/ signed main() { int n; float p; cin >> n >> p; int ps[1000001] = {0}; double total = 0.0; double q = 1.0 - p; FOR(i,2,n+1) { // 消されずに残っている確率を足す // 1->1.0, 2->(1-p) double k = pow(q, ps[i]); total += k; // 全ての数で篩を行う int j = i; while (j <= n) { ps[j]++; j += i; } } out("%.10lf\n", total); return 0; }