Modifying the value of variable declared as constant

Hi, I have declared the constant array for storing the data since I am having a limited RAM in lpc2214 now I want to put in the value in this array how it is possible in Keil UV3 for ARM. I have tried with doing it in,standard C way, but it dosent work. I am giving here the code example.

const int arr[12][900]
void main()
{
int i,j;
for(i=0;i<=12;i++)
{
for(j=0;j<=900;j++)
*(int *)&arr[i][j]=5;
}
}