Entrada de valores, soma diagonal Matriz, sum Matrix

#include
using namespace std;

int main()
{

int soma_diag=0, i, j, mat[3][3];

for (i=0; i<3 font="" i="">
  for (j=0; j<3 font="" j="">
  {
  cout << "Entre com o valor da Coluna " << i+1 << " e Linha " << j+1 << ": ";
  cin >> mat[i][j];
  if ( i == j ) soma_diag += mat[i][j]; // diag1
  if ( j == 3 - (i + 1) ) soma_diag += mat[i][j]; // diag2
  }
cout << soma_diag;

  system("PAUSE");
  return 0;