You have a collection of three jars, each of which contains some number of marbles. At any point, you can move marbles between jars as follows: if one jar has n marbles in it, you can move n marbles out of any other jar into that jar. For example, if one jar had 2 marbles, another 5, and another 7, then you could move two marbles out of th 5 or 7 jar into the 2 jar, or could move 5 marbles from the 7 jar into the two jar. You are told in advance that at least one of the jars contains exactly one marble. Devise a procedure to move marbles between jars so that at some point one of the jars becomes empty. (This puzzle taken from ACM SIGCSE)