[日常训练]curves

#include<cmath>
#include<ctime>
#include<stack>
#include<queue>
#include<cstdio>
#include<vector>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define eps 1e-10
#define M 1000
#define N 100005
using namespace std;
struct func{
    double a,b,c;
}a[N];
int n;
double l=0.0,r=1000.0,m1,m2;
inline double f(double x){
    double ret=a[1].a*x*x+a[1].b*x+a[1].c;
    for(int i=2;i<=n;++i)
        ret=max(ret,a[i].a*x*x+a[i].b*x+a[i].c);
    return ret;
}
inline void init(){
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
        scanf("%lf%lf%lf",&a[i].a,&a[i].b,&a[i].c);
    while(l+eps<r){
        m1=(r-l)/3.0;m2=l+m1*2.0;m1+=l;
        if(f(m1)>f(m2)) l=m1+eps;
        else r=m2;
    }
    printf("%.3lf\n",f(l));
}
int main(){
    freopen("curves.in","r",stdin);
    freopen("curves.out","w",stdout);
    init();
    fclose(stdin);
    fclose(stdout);
    return 0;
}