func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1000006, LG = 21, mod = 1e9 + 7, M = N;   const double eps = 1e-3, pi = acos(-1.0);   const long long INF = 1123456789123456789LL;   int main() {     string str;     cin >> str;     char mi =  a ;     bool ans = true;     for (char c : str)       if (c > mi + 1) {         ans = false;         break;       } else         mi = max(mi, c);     if (ans && str[0] ==  a )       printf( YES n );     else       printf( NO n );   }   