#include <cstdio>
#include <vector>
#include <random>
#include <algorithm>

const int T = 160000;

int N;
double PA, PB;
int A[20], B[20];
std::vector<int> va, vb;
std::random_device randomDevice;
std::mt19937 engine(randomDevice());

int simulate(int point_a, int point_b){
    if(va.empty()){
        return point_a > point_b;
    }

    int index, index2;
    if(va.size() == 1 || engine() % 1000 < PA * 1000){
        index = 0;
    }else{
        index = engine() % va.size();
    }

    if(vb.size() == 1 || engine() % 1000 < PB * 1000){
        index2 = 0;
    }else{
        index2 = engine() % vb.size();
    }

    int point = va[index] + vb[index2];
    if(va[index] > vb[index2]){
        point_a += point;
    }else if(va[index] < vb[index2]){
        point_b += point;
    }

    va.erase(va.begin() + index);
    vb.erase(vb.begin() + index2);

    return simulate(point_a, point_b);
}

int main(){ 
    scanf("%d %lf %lf", &N, &PA, &PB);

    for(int i=0;i<N;i++){
        scanf("%d", A+i);
    }

    for(int i=0;i<N;i++){
        scanf("%d", B+i);
    }

    std::sort(A, A+N);
    std::sort(B, B+N);

    double res = 0.0;
    for(int i=0;i<T;i++){
        va.resize(N);
        vb.resize(N);
        
        std::copy(A, A+N, va.begin());
        std::copy(B, B+N, vb.begin());
        
        res += simulate(0, 0);
    }

    printf("%.6f\n", 1. * res / T);
}