F -> a
S -> F | (S + F)
---
I      v
Input: (a + a)

I           v
Production: S
---
I      v
Input: (a + a)

I           v
Production: (S + F)
---
I       v
Input: (a + a)

I            v
Production: (S + F)
---
I       v
Input: (a + a)

I            v
Production: (a + F)
