Annual Parade

In the magic land, there is an annual parade hold on each spring. There are N cities in magic land, and M directed roads between cities. On the parade, there will be some(may be 0) heroes travel in this land, for each hero: He start at city begin[i], traveling to some cities, and finish at city end[i]. Note that: begin[i] may be equals to end[i], but he must at least moved to another city du