panic: runtime error: index out of range [-1]

goroutine 1 [running]:
main.solveEmbedded({0x40000fe4c0?, 0x34?})
	/tmp/cf-worker-129993432/verifierE.go:79 +0x680
main.main()
	/tmp/cf-worker-129993432/verifierE.go:394 +0x200