By Daniel Schweimler
BBC News, Buenos Aires
Residents of the Argentine capital Buenos Aires have plenty to worry about, like rising crime, the economy and increasing football hooliganism.
Small change could be a matter of life or death for the city's poor
But the most immediate daily concern of many portenos, as city residents are known, is how to make sure you have enough change for your bus fare home.
There are simply not enough coins minted and there is a serious shortage.
Bakeries may give you a small pastry or greengrocers an extra carrot instead of the 10 centavos change you are owed.
The trouble is, the chronic shortage of coins in the city can turn you into a liar. 'Have you got 25 centavos?' asks the shopkeeper.
No, you reply, nervously fingering the coins deep in your pocket. Just this 50-peso note.
Newspaper kiosks put up signs saying "No change".
Shops implore customers to pay with the exact money.
And if you should find your pocket weighed down with abundant coins and pay the exact money, do not be surprised if the shopkeeper falls at your feet in exaggerated gratitude.
Staff at an underground station recently allowed passengers in free since they had run out of change.
A spokesman said they ask the Argentine Central Bank for 45 million 10-centavo coins a year, but only get 24 million.
Buses only take coins, with machines eating up a fare of 80 valuable centavos - about 25 US cents. So you collect and hoard those valuable coins.
They may not be worth much in financial terms to many Buenos Aires residents - but they are life or death for the thousands of poor sales people, buskers and beggars who ply for trade on the Buenos Aires public transport system.
It leaves passengers with the constant moral dilemma of whether to give that very good, blind Bolivian guitar player the 50 centavos he so richly deserves to help feed his family - or save it for the bus fare home.