#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define MAX_N 100010 #define LOG 21 #define PI 3.141592653589 #define EPS 1e-6 #define MOD 1000000007 #define YJSNPI 810 #define INF (1 << 30) #define ADD(a, b) a = (a + (ll)b) % MOD #define MUL(a, b) a = (a * (ll)b) % MOD #define MAX(a, b) a = max(a, b) #define MIN(a, b) a = min(a, b) #define x first #define y second #define REP(i, a, b) for(int i = a; i < b; i++) #define RER(i, a, b) for(int i = a - 1; i >= b; i--) using namespace std; typedef long long ll; typedef pair pi; void debug() {cout << endl; } template void debug(FIRST arg, REST... rest) { cout << arg << " "; debug(rest...); } template void showary(T begin, T end) { while(begin != end) { cout << *begin << " "; begin++; } cout << endl; } double pa[50][50]; double pb[50][50]; double wina[50], winb[50]; double dp1[1 << 20]; double dp2[1 << 20]; double dp[50][50][50]; int va[50], vb[50]; int N; double A, B; void solve(double *dp, double (*p)[50], double A) { dp[0] = 1.0; REP(bit, 0, (1 << N)) { int cnt = 0, minat = -1; REP(i, 0, N) { if(bit & (1 << i)) cnt++; else if(minat == -1) minat = i; } if(cnt == N - 1) p[cnt][minat] += dp[bit]; else p[cnt][minat] += dp[bit] * A; dp[bit | (1 << minat)] += dp[bit] * A; REP(i, 0, N) { if((bit & (1 << i)) || minat == i) continue; if(N - cnt - 1 > 0) p[cnt][i] += dp[bit] * (1.0 - A) / (N - cnt - 1.0); if(N - cnt - 1 > 0) dp[bit | (1 << i)] += dp[bit] * (1.0 - A) / (N - cnt - 1.0); } } } int main() { cin >> N >> A >> B; REP(i, 0, N) cin >> va[i]; REP(i, 0, N) cin >> vb[i]; sort(va, va + N); sort(vb, vb + N); solve(dp1, pa, A); solve(dp2, pb, B); double res = 0; REP(i, 0, N) { REP(j, 0, N) { REP(k, 0, N) { if(va[j] > vb[k]) { res += pa[i][j] * pb[i][k] * (va[j] + vb[k]); } } } } /* REP(i, 0, N) showary(pa[i], pa[i] + N); REP(i, 0, N) showary(pb[i], pb[i] + N); showary(wina, wina + N); showary(winb, winb + N); */ printf("%.10f\n", res); }