Iterate over all possible pairs of the array pows [ ]
for ( int i = 0 ; i < pows . size ( ) ; i ++ ) { for ( int j = 0 ; j < pows . size ( ) ; j ++ ) { if ( pows . get ( i ) + pows . get ( j ) <= R && pows . get ( i ) + pows . get ( j ) >= L ) {