func_code_string: #include <bits/stdc++.h>   using namespace std;   long long gcd(long long x, long long y) { return (!y ? x : gcd(y, x % y)); }   long long lcm(long long x, long long y) { return x / gcd(x, y) * y; }   void file() {}   void fast() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     file();   }   int dx[] = {-1, 0, 1, 0};   int dy[] = {0, 1, 0, -1};   const double eps = 1e-9;   const int mod = 1e9 + 7;   const int N = 1e5 + 5;   int n;   string s;   int dp[N][10][2];   int upd(int x) {     int sum = 0;     while (x) sum += x % 10, x /= 10;     return sum;   }   int solve(int idx, int sum, bool ok) {     if (idx == n) {       if (sum % 3 == 0) return 0;       return 1e9;     }     int &ret = dp[idx][sum][ok];     if (~ret) return ret;     ret = solve(idx + 1, sum, ok) + 1;     if (ok || s[idx] !=  0 )       ret = min(ret, solve(idx + 1, upd(sum + s[idx] - 48), 1));     return ret;   }   void solve2(int idx, int sum, bool ok) {     if (idx == n) {       return;     }     int &ret = dp[idx][sum][ok];     if (ret == solve(idx + 1, sum, ok) + 1) {       solve2(idx + 1, sum, ok);       return;     }     cout << s[idx];     solve2(idx + 1, upd(sum + s[idx] - 48), 1);     return;   }   int main() {     fast();     memset((dp), -1, sizeof(dp));     cin >> s;     n = (int)s.size();     bool ok = 0;     for (int i = 0; i < (int)s.size(); i++) {       ok |= s[i] ==  0 ;     }     int x = solve(0, 0, 0);     if (x == n) {       if (!ok)         cout << -1;       else         cout << 0;       return 0;     }     solve2(0, 0, 0);     return 0;   }   