Given a specific sequence of dominoes (assume it is a DAG) represented by:
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1 line containing 2 integers: the number n of tiles (n>=2) and the number of dependencies m to be described (m>=0)
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m lines containing 2 integers x and y indicating that if tile x falls, then tile y also falls.
Return two integers k and l, where k is the minimum number of interventions needed to guarantee that all dominoes fall e l is the size of the largest sequence of falling dominoes.