It is a loan-calculator program for calculation of a loan on a house or a car.
The distinctive feature of this calculator is the ability to see the overpayment to bank,
which goes on payment of interest on a loan.
You are inputting the sum of a loan, a bank's interest rate, and monthly payment,
which you are going to pay, and a program computes the total time of payment,
overpayment and the overall sum.
The accuracy of calculation formula had been approving at a bank's forum.