DO NOT LOOP the program. It should end after $1$ execution.

Sample Output

Enter $5$ grades:

$23\mathrm{.}4$

$-99$

ERROR: Invalid grade

$78$

$32$

$99$

$100$

Grade $1$: F

Grade $2$: C

Grade $3$: F

Grade $4$: A

Grade $5$: A

Average: $66\mathrm{.}48\%$

Letter Grade: $0$