Function to return the sum of the cells arr [ i1 ] [ j1 ] and arr [ i2 ] [ j2 ]
def sum ( i1 , j1 , i2 , j2 ) : NEW_LINE INDENT if ( i1 == i2 and j1 == j2 ) : NEW_LINE INDENT return arr [ i1 ] [ j1 ] NEW_LINE DEDENT return arr [ i1 ] [ j1 ] + arr [ i2 ] [ j2 ] NEW_LINE DEDENT