#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
int t;
while(cin>>t)
{
double n,m,sum1=0,sum2=0; //sum1求学分和,sum2求学分乘绩点和
while(t--)
{
cin>>n>>m;
if(m==-1)
continue;
sum1+=n;
if(m>=90) m=4;
else if(m>=80) m=3;
else if(m>=70) m=2;
else if(m>=60) m=1;
else if(m<60) m=0;
sum2+=m*n;
}
if(sum1<=0||sum2<=0)
{
cout<<"-1"<<endl;
continue;
}
cout<<setprecision(2)<<std::fixed<<sum2/sum1<<endl;
}
return 0;
}
杭电acm1202 求GPA
最新推荐文章于 2021-07-02 12:53:43 发布