Insertion Sort Array C++ Program in Efficient Way

#include<bits/stdc++.h> //to include all header file
using namespace std;
main()
{
int n,i,j,k;
cout<<"Enter Size of Array:";
cin>>n;

int a[n];

cout<<"Enter Elements Into Array:";
for(i=0;i<n;i++)
cin>>a[i];

for(i=0;i<n-1;i++)
{
j=i;
while(j>=0&&a[j]<a[j+1])
{
swap(a[j],a[j+1]); //pre-defined function in STL
j--;
}
}
for(i=0;i<n;i++)
{
cout<<a[i];
}
}