CF739E Gosha is hunting

#include<bits/stdc++.h>
#define reg register int
#define il inline
#define fi first
#define se second
#define mk(a,b) make_pair(a,b)
#define num (ch^‘0‘)
using namespace std;
typedef long long ll;
template<class T>il void rd(T &x){
    char ch;x=0;bool fl=false;
    while(!isdigit(ch=getchar()))(ch==‘-‘)&&(fl=true);
    for(x=num;isdigit(ch=getchar());x=x*10+num);
    (fl==true)&&(x=-x);
}
template<class T>il void output(T x){if(x/10)output(x/10);putchar(x%10+‘0‘);}
template<class T>il void ot(T x){if(x<0) putchar(‘-‘),x=-x;output(x);putchar(‘ ‘);}
template<class T>il void prt(T a[],int st,int nd){for(reg i=st;i<=nd;++i) ot(a[i]);putchar(‘\n‘);}

namespace Miracle{
const int N=2002;
const double eps=1e-10;
int numa[N],numb[N];
int n,a,b;
double p[N],u[N];
double dp[N];
void wrk(double ca,double cb){
    for(reg i=1;i<=n;++i){
        dp[i]=dp[i-1];numa[i]=numa[i-1];numb[i]=numb[i-1];
        if(dp[i]<dp[i-1]+p[i]-ca-eps){
            dp[i]=dp[i-1]+p[i]-ca;numa[i]=numa[i-1]+1;numb[i]=numb[i-1];
        }
        if(dp[i]<dp[i-1]+u[i]-cb-eps){
            dp[i]=dp[i-1]+u[i]-cb;numb[i]=numb[i-1]+1;numa[i]=numa[i-1];
        }
        if(dp[i]<dp[i-1]+u[i]+p[i]-p[i]*u[i]-ca-cb-eps){
            dp[i]=dp[i-1]+u[i]+p[i]-p[i]*u[i]-ca-cb;numb[i]=numb[i-1]+1;numa[i]=numa[i-1]+1;
        }
    }
}
double che(double ca){
    double l=0,r=1;
    for(reg i=1;i<=50;++i){
        double mid=(l+r)/2;
        wrk(ca,mid);
        if(numb[n]>b){
            l=mid;
        }else{
            r=mid;
        }
    }
    return (l+r)/2;
}
int main(){
    rd(n);rd(a);rd(b);
    for(reg i=1;i<=n;++i){
        scanf("%lf",&p[i]);
    }
    for(reg i=1;i<=n;++i){
        scanf("%lf",&u[i]);
    }
    double l=0,r=1,ka,kb;
    for(reg i=1;i<=50;++i){
        double mid=(l+r)/2;
        kb=che(mid);
        if(numa[n]>a){
            l=mid;
        }else{
            r=mid;
        }
    }
    ka=(l+r)/2;
    wrk(ka,kb);
    printf("%.10lf",dp[n]+ka*a+kb*b);
    return 0;
}

}
signed main(){
    Miracle::main();
    return 0;
}

/*
   Author: *Miracle*
   Date: 2019/3/22 20:22:58
*/