custom OnConflictStrategy using Room DB

I'd like to set my own conflict columns not default primary key (just an auto increment integer in my case). So my table is:

@Entity(tableName = "users_tab")
data class User(
    @PrimaryKey(autoGenerate = true)
    var id: Int,
    var str1: String,
    var str2: String,
    var str3: String
)

@Dao
interface UserDAO {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(users: List<User>)

}

I'd like to REPLACE when User has same str1 and str2 how should I modify my Insert adnotation?