m = m0 + 1, ('4' ' + '5' ' + '6' ' + '7' ' + '8' ' + '9' ')[m0] ' = "0", m < 7 ⊦ m = 0
Used simplifier rules: n ≠ 0 ⊦ m = n - 1 ↔ n = m + 1; (elim) Used terms: m, m0