#include<bits/stdc++.h>
#pragma GCC optimize(2)
#define	int	long long
using namespace std;
int p,n;char a[1009];string s;
set<int>s1;map<char,int>mp;
signed main()
{
	getline(cin,s);
	for(auto i:s)
	{
		if(('a'<=i&&i<='z')||i=='|'||i=='!'||i=='^'||i=='&')
		{
			a[++n]=i;
			if('a'<=i&&i<='z')s1.insert(i);
		}
	}
	int m=s1.size(),p1=1;
	for(int i=1;i<=m;i++)
	{
		p1*=2;
	}
	for(int i=0;i<p1;i++)
	{
		int k=i;
		for(auto c:s1)
		{
			mp[c]=k%2;
			k/=2;
		}
		stack<int>sx;
		for(int j=1;j<=n;j++)
		{
			if('a'>a[j]||'z'<a[j])
			{
				if(a[j]=='!')
				{
					int x=sx.top();
					sx.pop();
					sx.push(!x);
					continue;
				}
				int x=sx.top();sx.pop();int y=sx.top();sx.pop();
				if(a[j]=='&')sx.push(x&y);
				else if(a[j]=='|')sx.push(x|y);
				else if(a[j]=='^')sx.push(x^y);
			}
			else sx.push(mp[a[j]]);
		}
		if(sx.top()==0)
		{
			cout<<"NO";
			return 0;
		}
	}
	cout<<"YES";
	return 0;
}