Grammar for ${a^n b^n c^{n+m}}$
GRAMMAR FOR THE LANGUAGE:{a^n b^n c^n/n>=1}

S->abc|A

A->aABc|abc

cB->Bc

bB->bb

FOR EXAMPLE:INPUT STRING aaabbbccc when n=3

S->A

->aABc

->aaABcBc (A->aABc)

->aaabcBcBc   (A->abc)

->aaabBccBc   (cB->Bc)

->aaabBcBcc   (cB->Bc)

->aaabbcBcc   (bB->bb)

->aaabbBccc   (cB->Bc)

->aaabbbccc   (bB->bb)