func_code_string: #include <bits/stdc++.h>   using namespace std;   long long w, m, k;   long long comp;   long long getpre(long long a) {     long long tmp = 1, ct = 0;     while (a >= tmp) tmp *= 10, ++ct;     tmp /= 10;     long long t = 1;     long long ans = 0;     for (long long i = 1; i < ct; ++i) ans += i * 9 * t, t *= 10;     ans += (a - tmp + 1) * ct;     return ans;   }   bool judge(long long len) {     long long tl = m - 1;     long long tr = m + len - 1;     if (getpre(tr) - getpre(tl) <= comp) return true;     return false;   }   int main() {     cin >> w >> m >> k;     long long l = 0, r = w / k + 1, ans = 0;     comp = r - 1;     while (l <= r) {       long long mid = (l + r) >> 1;       if (judge(mid))         l = mid + 1, ans = mid;       else         r = mid - 1;     }     cout << ans << endl;   }   