| key ∈ keys(fs, ax0) → (∃ ax2, ax1, adr. ax0 = ax2 + adr ' + ax1 ∧ fs[adr].key = key ∧ ¬ fs[adr].key ∈ keys(fs, ax1)), key = fs[adr].key ∨ key ∈ keys(fs, ax0) ⊦ ∃ ax, ax1, adr0. adr ' + ax0 = ax + adr0 ' + ax1 ∧ fs[adr0].key = key ∧ ¬ fs[adr0].key ∈ keys(fs, ax1) |
key ∈ keys(fs, ax0) → ax0 = ax + adr0 ' + ax1 ∧ fs[adr0].key = key ∧ ¬ fs[adr0].key ∈ keys(fs, ax1), key = fs[adr].key ∨ key ∈ keys(fs, ax0) ⊦ ∃ ax, ax1, adr0. adr ' + ax0 = ax + adr0 ' + ax1 ∧ fs[adr0].key = key ∧ ¬ fs[adr0].key ∈ keys(fs, ax1)