Statement

Filippo decided to fund a new oil company, and now he is looking for new underground oil fields. Using a new technology, he has been able to map the underground oil deposits to a matrix of N rows and M columns. Each cell of the matrix contains a value 0 or 1, representing the absence or presence of oil, respectively. An oil field is a rectangular area in the matrix such that each cell in the oil field contains the value 1. An oil field is called profitable if it contains every cell in the matrix having value 1. Can you help Filippo by telling him whether the matrix contains a profitable oil field?