Ошибка Constant expression required. Как исправить?

    double a[n][n+1];          
            double x[n];

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{
    cout.precision(4);
    cout.setf(ios::fixed);
    int n,i,j,k,flag=0,count=0;
    cout<<"\nEnter the no. of equations\n";
    cin>>n;                    //Input no. of equations
    double a[n][n+1];            //declare a 2d array for storing the elements of the augmented matrix
    double x[n];                //declare an array to store the values of variables
    double eps,y;
    cout<<"\nEnter the elements of the augmented matrix row-wise:\n";
    for (i=0;i<n;i++)
        for (j=0;j<=n;j++)
            cin>>a[i][j];
    cout<<"\nEnter the initial values of the variables:\n";
    for (i=0;i<n;i++)
        cin>>x[i];
    cout<<"\nEnter the accuracy upto which you want the solution:\n";
    cin>>eps;
    for (i=0;i<n;i++)                    //Pivotisation(partial) to make the equations diagonally dominant
        for (k=i+1;k<n;k++)
            if (abs(a[i][i])<abs(a[k][i]))
                for (j=0;j<=n;j++)
                {
                    double temp=a[i][j];
                    a[i][j]=a[k][j];
                    a[k][j]=temp;
                }
    cout<<"Iter"<<setw(10);
    for(i=0;i<n;i++)
        cout<<"x"<<i<<setw(18);
    cout<<"\n----------------------------------------------------------------------";
    do                            //Perform iterations to calculate x1,x2,...xn
    {
        cout<<"\n"<<count+1<<"."<<setw(16);
        for (i=0;i<n;i++)                //Loop that calculates x1,x2,...xn
        {
            y=x[i];
            x[i]=a[i][n];
            for (j=0;j<n;j++)
            {
                if (j!=i)
                x[i]=x[i]-a[i][j]*x[j];
            }
            x[i]=x[i]/a[i][i];
            if (abs(x[i]-y)<=eps)            //Compare the ne value with the last value
                flag++;
            cout<<x[i]<<setw(18);
        }
        cout<<"\n";
        count++;
    }while(flag<n);                        //If the values of all the variables don't differ from their previious values with error more than eps then flag must be n and hence stop the loop
 
    cout<<"\n The solution is as follows:\n";
    for (i=0;i<n;i++)
        cout<<"x"<<i<<" = "<<x[i]<<endl;        //Print the contents of x[]
    return 0;
}

const int m = 5;
const int n = 10; 
double a[m][n];