panic: invalid argument to Intn

goroutine 1 [running]:
math/rand.(*Rand).Intn(0x40000a0b08?, 0x80b64?)
	/usr/local/go/src/math/rand/rand.go:180 +0x64
main.randomTest(0x40000edca0)
	/home/ubuntu/codeforces/1000-1999/1200-1299/1260-1269/1266/verifierE.go:188 +0x128
main.generateTests()
	/home/ubuntu/codeforces/1000-1999/1200-1299/1260-1269/1266/verifierE.go:169 +0x27c
main.main()
	/home/ubuntu/codeforces/1000-1999/1200-1299/1260-1269/1266/verifierE.go:47 +0x10c
exit status 2