```
java ru.fizteh.fivt.students.piakovenko.calculator.Calculator ()
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
	at java.util.ArrayList.rangeCheck(ArrayList.java:604)
	at java.util.ArrayList.get(ArrayList.java:382)
	at ru.fizteh.fivt.students.piakovenko.calculator.Tree.buildCalculationTree(Tree.java:87)
	at ru.fizteh.fivt.students.piakovenko.calculator.Tree.parseCalculationTree(Tree.java:92)
	at ru.fizteh.fivt.students.piakovenko.calculator.Tree.parseExpressionNodes(Tree.java:32)
	at ru.fizteh.fivt.students.piakovenko.calculator.Tree.parseCalculationTree(Tree.java:91)
	at ru.fizteh.fivt.students.piakovenko.calculator.Calculator.main(Calculator.java:36)
```