前面的基本都能A 最后一个点tle，稍微加点优化就行了
```cpp
#include<iostream>
#include<cstring>
#include<cstdio>
#define N 500010
#define inf 100000008
using namespace std;

int n;
double k[N],s[N],u[N],Eu,v[N];

bool check(double a,double b,int i){
return 2.0*a*k[i]*b*b*(b-u[i])<=1.0?true:false;
}

double TwoPoint(int i,double lambda){
double l=max(u[i],0.0),r=inf,mid;
for(int j=1;j<=100;++j){
mid=(l+r)/2;
if(check(lambda,mid,i))l=mid;
else r=mid;
}
return mid;
}

bool Check(double mid){
double E=0;
for(int i=1;i<=n;++i)v[i]=TwoPoint(i,mid);
for(int i=1;i<=n;++i)E+=k[i]*s[i]*(v[i]-u[i])*(v[i]-u[i]);
return E>=Eu;
}

int main(){
scanf("%d",&n);
scanf("%lf",&Eu);
for(int i=1;i<=n;++i)
scanf("%lf%lf%lf",&s[i],&k[i],&u[i]);
double l=0.0,r=inf,mid;
for(int j=1;j<=100;++j){
mid=(l+r)/2;
if(Check(mid))l=mid;
else r=mid;
}
double ans=0;
for(int i=1;i<=n;++i)
ans+=s[i]/v[i];
printf("%.8f\n",ans);
return 0;
}
```

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