Input (grade 13): It runs in a crescent through Mali, Niger, on the border with Benin and then through Nigeria, discharging through a massive delta, known as the Niger Delta or the Oil Rivers, into the Gulf of Guinea in the Atlantic Ocean.
Output (grade 6): It has a crescent shape and it goes through Guinea, Mali, Niger, on the border with Benin and then through Nigeria. Finally, it reaches the sea at a large delta, called the Niger Delta of the Oil Rivers.