def shu_osher_change_alpha_ij(alpha,beta,i,j,val):
    """
        **Input**:
            - alpha, beta: Shu-Osher arrays
            - i,j: indices
            - val -- real number

        **Output**: Shu-Osher arrays alph, bet with alph[i,j]=alpha[i,j]+val.
    """
    alpha[i,j] = alpha[i,j]+val
    alpha[i,:] -= val*alpha[j,:]
    beta[i,:]  -= val* beta[j,:]
    return alpha,beta