st.min ∈ st ⊦ st = ∅, st.keys.min ∈ st
Used simplifier rules: Min-in: ⊦ st ≠ ∅ → st.min ∈ st;%Min-min: ⊦ a ∈ st → ¬ a < st.min;%inf: ⊦ a ∈ st → a ∈ st.keys;%Keys: ⊦ a ∈ st.keys ↔ a ∈ st;% ⊦ ¬ a < a; (s)