1)Look at my solution 7450309 (Runtime error (non-zero exit code) on test 23)) and 7450312(AC). Why i got Runtime error (non-zero exit code) on test 23?
  In first solution i have nmax=123456 and in second 223456. What is range of n?

2)Look on problem 1974. In forum i wrote test when my AC solution get wrong answer(I can write more tests where my old AC solution falls)