Letters and numbers take turns in the series B, 40, E, 36, I, 31, N. What number comes next?

Letters and numbers alternate, each keeping its own rule. The letters B 2, E 5, I 9, N 14 go on by 3, then 4, then 5 places. The numbers 40, 36, 31 fall by 4 and then by 5, so the next fall is 6 and the number is 31 − 6 = 25. The trap 26 repeats the previous fall of 5, the trap 27 repeats the fall of 4, and the trap 24 jumps ahead to a fall of 7.