Gym

Gym - 100941G

https://vjudge.net/problem/Gym-100941G
比赛的时候真的是不会啊，那就没办法了。
结论：每x周减一次头发，第k次剪发时的头发长度为x^k。
x^k=L,x=L^(1/k)
ans=kx=k*L^(1/k)

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstring>
#define inf 2147483647
#define N 1000010
#define p(a) putchar(a)
#define For(i,a,b) for(int i=a;i<=b;++i)

using namespace std;
double ans,L;
void in(int &x){
    int y=1;char c=getchar();x=0;
    while(c<'0'||c>'9'){if(c=='-')y=-1;c=getchar();}
    while(c<='9'&&c>='0'){ x=(x<<1)+(x<<3)+c-'0';c=getchar();}
    x*=y;
}
void o(int x){
    if(x<0){p('-');x=-x;}
    if(x>9)o(x/10);
    p(x%10+'0');
}

signed main(){
    freopen("princess.in","r",stdin);
    freopen("princess.out","w",stdout);
    cin>>L;
    ans=1e9;
    For(k,1,400)
        ans=min(ans,(double)k*pow(L,1.0/(double)k));
    printf("%.6f",ans);
    return 0;
}