Balancing

#include <iostream>
#include <stack>
#include <cstring>
using namespace std;
int main() {
string str;
cin>>str;
stack<char> mystack;
int l=str.size();
bool flag=true;
//cout << str << "\n";
int ref;
for (int i=0; i<l; i++) {
if (mystack.size()==0) {
mystack.push(str[i]);
continue;
}
ref=(int)str[i];
if (ref>(int)mystack.top()) {
if (ref-mystack.top() <=2) {
mystack.pop();
}
else {
cout << "NO\n";
return 0;
}
}
else {
mystack.push(str[i]);
}
}
if (mystack.size()==0) {
cout << "YES\n";
}
else {
cout << "NO\n";
}
return 0;
}