panic: invalid argument to Intn

goroutine 1 [running]:
math/rand.(*Rand).Intn(0x0?, 0xe?)
	/usr/local/go/src/math/rand/rand.go:180 +0x64
main.genTest(0x400006ce90)
	/home/ubuntu/codeforces/1000-1999/1300-1399/1380-1389/1389/verifierG.go:147 +0x60
main.main()
	/home/ubuntu/codeforces/1000-1999/1300-1399/1380-1389/1389/verifierG.go:222 +0x180
exit status 2