#include <iostream>
#include<cmath>
int n;
int a[100];
int s;

using namespace std;

int main()
{
    cout << "moi ban nhap n";
    cin>>n;
    int s=0;
    for(int i=1;i<=n;i++)
        cin >> a[i];

    for(int i=1;i<=n;i++)
        if((a[i]-1)%3==0)
        s=s+a[i];
        cout<<"tong cac so co dang 3k+1 "<<s;
    return 0;
}