#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
struct node
{
	node *lchild=nullptr,*rchild=nullptr;
	char chr;
	bool b=false;
}; 
set<char>S;
vector<char>V;
map<char,int>mp;
int get(int a,int b,char c)
{
	if(c=='|')
		return a|b;
	else if(c=='&')
		return a&b;
	else 
		return a^b;
}
int check(node* ans)
{
	if(ans->chr=='|'||ans->chr=='&'||ans->chr=='^')
		if(!ans->b)
			return get(check(ans->lchild),check(ans->rchild),ans->chr);
		else
			return !get(check(ans->lchild),check(ans->rchild),ans->chr);
	else
	{
		if(!ans->b)
			return mp[ans->chr];
		else
			return !mp[ans->chr];
	}
			
}
int end_depth;
set<int>lk;
node* root;
void DFS(int depth)
{
	if(depth==end_depth)
	{
		lk.insert(check(root));
		return;
	}
	else
	{
		mp[V[depth]]=0;
		DFS(depth+1);
		mp[V[depth]]=1;
		DFS(depth+1);
	} 
}
int main()
{
	string str;
	getline(cin,str);
	stack<node*>st;
	int length=str.size();
	for(int i=0;i<length;i++)
	{
		if(str[i]==' ')
			continue;
		else if(str[i]=='|'||str[i]=='&'||str[i]=='^')
		{
			node* lc=st.top();
			st.pop();
			node* rc=st.top();
			st.pop();
			node* top=new node;
			top->chr=str[i];
			top->lchild=lc;
			top->rchild=rc;
			st.push(top);
		}
		else if(str[i]=='!')
		{
			node* top=st.top();
			st.pop();
			top->b=!top->b;
			st.push(top);
		}
		else
		{
			S.insert(str[i]);
			node* top=new node;
			top->chr=str[i];
			st.push(top);
		}
	}
	for(auto p:S)
		V.push_back(p);
	end_depth=V.size();
	root=st.top();
	st.pop();
	DFS(0);
	if(lk.count(0))
		cout<<"NO";
	else
		cout<<"YES";
	return 0;
}