MathDB

There are coins worth

1, 2, \ldots , b

rubles, blue bills with worth

a{}

rubles and red bills worth

a + b

rubles. Ilya wants to exchange a certain amount into coins and blue bills, and use no more than

a-1

coins. Pasha wants to exchange the same amount in coins and red bills, but use no more than

a{}

coins. Prove that they have equally many ways of doing so.

Problem Statement