can any one plz explain me y i am getting 6 and 7 has a value of 38 and 7

Question

#include<iostream>
using namespace std;
int main()
{
int a[]={1,3,5,6};
for(int x=1;x<10;x++)
{
a[x];
cout<<x<<":"<<a[x]<<endl;
}
}
//OUT PUT
1:3
2:5
3:6
4:0
5:0
6:38
7:7
8:0
9:0
//Y I AM GETTING 6&7 HAS 38 AND 7

Answer 1

it takes garabage values for it

Answer 2

if you execute this code ones again the values are different

Answer 3

but still iam getting same values...