It's not so unusual to run out of someone else's currency.

Development Economics Blackwell PubliJeffrey Sachsrs ISBN 0-8133-3314-8
Sachs Jeffrey and Pistor Katharina. From 2002 to 2006 he was Director of the United Nations Millennium Project's work on the Millennium Development Goals eight internationally sanctioned objectives to reduce extreme poverty hunger and disease by the year 2015. He is a member of the Institute of Medicine; the American Academy of Arts and Sciences; Harvard Society of Fellows; the Fellows of the World Econometric Society; the Brookings Panel of Economists; the National Bureau of Economic Research; and the Board of Advisers of the Chinese Economists Society among other international organizations.

He is Director of the UN Sustainable Development Solutions Network. Subsequently he has been known for his work on the challenges of economic development environmental sustainability poverty alleviation debt cancellation and globalization. Jeffrey David Sachs (/ˈsæks/; born November 5 1954) is an American economist and Director of The Earth Institute at Columbia University.