CodeForces782B The Meeting Place Cannot Be Changed 三分查找

The main road in Bytecity is a straight line from south to north. Conveniently, there are coordinates measured in meters from the southernmost building in north direction.

At some points on the road there are n friends, and i-th of them is standing at the point xi meters and can move with any speed no greater than vi meters per second in any of the two directions along the road: south or north.

You are to compute the minimum time needed to gather all the n friends at some point on the road. Note that the point they meet at doesn't need to have integer coordinate.

Input

The first line contains single integer n (2 ≤ n ≤ 60 000) — the number of friends.

The second line contains n integers x1, x2, ..., xn (1 ≤ xi ≤ 109) — the current coordinates of the friends, in meters.

The third line contains n integers v1, v2, ..., vn (1 ≤ vi ≤ 109) — the maximum speeds of the friends, in meters per second.

Output

Print the minimum time (in seconds) needed for all the n friends to meet at some point on the road.

Your answer will be considered correct, if its absolute or relative error isn't greater than 10 - 6. Formally, let your answer be a, while jury's answer be b. Your answer will be considered correct if  holds.

Examples

input

37 1 31 2 1

output

2.000000000000

input

45 10 3 22 3 2 4

output

1.400000000000

Note

In the first sample, all friends can gather at the point 5 within 2 seconds. In order to achieve this, the first friend should go south all the time at his maximum speed, while the second and the third friends should go north at their maximum speeds.

一直线上n个人到同一个点的最大时间最小，可以使用二分或三分查找位置，最后求得时间。

#include <iostream>#include <cstdio>#include <map>#include <set>#include <vector>#include <queue>#include <stack>#include <cmath>#include <algorithm>#include <cstring>#include <string>using namespace std;#define INF 0x3f3f3f3ftypedef long long LL;double x[60005],v[60005];int n;double f(double m){    double time=0;    for(int i=1;i<=n;i++){        time=max(time,fabs((x[i]-m))/v[i]);    }    return time;}int main(){    while(cin>>n){        double l=INF,r=0,m;        for(int i=1;i<=n;i++){            cin>>x[i];            l=min(l,x[i]);            r=max(r,x[i]);        }        for(int i=1;i<=n;i++){            cin>>v[i];        }        while(r-l>0.0000001){            double ll=(2*l+r)/3,rr=(l+2*r)/3;            double f1=f(ll),f2=f(rr);            if(f(r)==f(l)){                if(f1==f2){                    l=ll;                    r=rr;                }else if(f1<f2){                    l=ll;                }else{                    r=rr;                }            }else if(f(r)>f(l)){                if(f1==f2){                    l=ll;                    r=rr;                }else if(f1<f2){                    r=rr;                }else{                    l=ll;                }            }else{                if(f1==f2){                    l=ll;                    r=rr;                }else if(f1<f2){                    r=rr;                }else{                    l=ll;                }            }        }        printf("%.6lf",f(r));    }    return 0;}