I'm new to natural deduction and am attempting a question which sounds like the Sorites paradox: 1 million grains of sand is a heap. If 1 million grains of sand is a heap, then 999,999 grains is a heap. If 999,999 grains is a heap then 999,998 grains is a heap...2 grains is a heap, therefore 1 grain of sand is a heap. (paraphrased) There is an implicit premise that "a heap of sand -1 grain is still a heap" which is premise A.
I have formalised the premises as: $A$, $(A∧B)→C$, $(A∧C)→D$, $(A∧E)→F$ therefore $F$
Is it possible to show this is valid through Fitch-style natural deduction?