Homework 3 - calc
Revert "Homework 3 - calc"

This reverts commit d8294610cfa4afa26814d589e5e20d5debe4f746.
Homework3 - calculator
Revert "Homework3 - calculator"

This reverts commit 43ccfea38d0bf4cc6a95b8dc98f1028ef1061815.
Homework3 - calculator
homework_4
Merge pull request #178 from Marina97/master

Homework 4