报错了，看看为啥？

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
    int sum=0,dd=1;
    struct renwu
    {
        int id,shijian;
    };
    renwu a[100001];
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i].shijian;
        sum+=a[i].shijian;
        a[i].id=dd;
        dd++;
    }
    sort(a+1,a+n+1);
    cout<<sum;
    for(int i=1;i<=n;i++)
    {
        cout<<a[i].id;
    }
}