Simple RPN Calulator

This is a simple calculator for the UPN principle (Reverse Polish Notation) works. Inspired by the many products from Hewlett-Packard for this area.
Some features:
- It has all the basic arithmetic operations and can also squares and calculates root
- The stack comprises four levels and is always visible
- Automatic switching between German and English, depending on the setting of the device
- Import and export values via the clipboard
- Landscape mode
- Accuracy of ~15 digits
- Ad-free