请先理解代码

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cctype>
#include<cstring>
#include<string>
#include<vector>
#include<set>
#include<stack>
#include<queue>
#include<iostream>
#include<iomanip>
#include<ctime>
#include<algorithm>
#include<map>
using namespace std;
int main(){
    int n;
    double sum=0.0;
    cin>>n;
    for(int i=1;i<=n;i++){
        int a;
        cin>>a;
        sum+=a;
    }
    // cout<<sum<<endl;
    printf("%.2f",sum/n);
}