There are countless ways to teach a kid mathematics: fingers, peas in bowls, catchy songs — or, like this Italian grandpa from Partinico, Sicily, by counting dirty money.

As Italian daily La Stampa reports, after taking his nine-year-old granddaughter to school or to the swimming pool, the suspected mobster would sell cocaine. Later, after the deal was done, he would turn to the girl to help tally up his daily gains, using her as his personal cashier-in-training as he taught her to count bills.

The elementary school student also worked part-time as a "mule," carrying the drug money in her pockets, to hide his activities from the authorities as well as from their own family.

The Sicilian police eventually caught wind of the operation and put a tap on the drug-smuggling grandpa. This, as Partinico commissioner Leopoldo Laricchia told reporters, led to the recording of surreal exchanges between the granddaughter and her grandfather.

Having figured out there was something shady behind "grandpa's funny game," the little girl reportedly told him one day as they were watching TV together: "Look Grandpa, they're selling drugs to people, just like we do!"

The man was arrested earlier this week, along with 29 other people as part of a large-scale anti-drug operation in the Palermo region. According to daily La Repubblica, the girl's mother "severely scolded" the grandfather after learning about his special math lessons.

With the investigation still ongoing, there's no word yet on a fine or prison sentence for the Nonno — but that's something he'll have to count on his own.