Required Length
int main() { int rs = 0; ull x; int n; cin >> n; cin >> x; if (x == 1 && n > 1) { cout << -1 << endl; return; } int num = log10(x) + 1; while (num < n) { int max_char = 0; ull l = x; for (int i = 0; i < num; i++) { max_char = max(max_char, static_cast<int>(l % 10)); l /= 10; } x *= max_char; rs++; num = log10(x) + 1; } cout << rs << endl; }
Source: codeforces.com