accumulate
#include<iostream>
#include<vector>
#include<numeric>
using namespace std;
int main()
{
vector<double> vec;
double i;
while(cin>>i)
vec.push_back(i);
int sum = accumulate(vec.begin(),vec.end(),0);
/*计算结果转换成int类型,怎么处理,写成0.0或者double(0.0)都不行*/
cout<<" sum = "<<sum<<endl;
return 0;
}