C++ :

#include<iostream>
#include<stack>
#include<cstdio>
#include<cstring>
using namespace std;

string s;
char x[200];
int sz[200],t=0,r=0;
stack<char> fuhao;

void work(string s);
bool check(string s);

int main()
{
	//freopen("test.in","r",stdin);
	int z,j1,j2;
	cin>>s;
	if (check(s))
	{
		work(s);
		for (int i=0;i<t;i++)
	    {
		  if(x[i]<'0' && x[i]!=' ')
	  	  {
			z=i-1; 
			while (x[z]==' ') z--;
			j1=sz[x[z]-'0'];
			x[z]=' ';
			z=i-2; 
			while (x[z]==' ') z--;
			j2=sz[x[z]-'0'];
			x[z]=' ';
			
			if (x[i]=='+') 
			{
				sz[r]=j1+j2;
				x[i]='0'+r;
				r++;
			}
			else if (x[i]=='-') 
			{
				sz[r]=j2-j1;
				x[i]='0'+r;
				r++;
			}
			else if (x[i]=='*') 
			{
				sz[r]=j1*j2;
				x[i]='0'+r;
				r++;
			}
			else if (x[i]=='/') 
			{
				sz[r]=j2/j1;
				x[i]='0'+r;
				r++;
			}
		  }
	    }
	cout<<sz[r-1];
	}
	else cout<<"NO";	
	
	return 0;
}

bool check(string s)
{
	int i=0,kuohao=0;
	while (s[i]!='@')
	{
		if (s[i]=='(') kuohao++;
		if (s[i]==')' && kuohao==0) return false;
		else kuohao--;
		if (i==0 && (s[i]=='*' || s[i]=='/')) return false;
		if (s[i]<'0' && s[i+1]<'0' && s[i]>='*' && s[i+1]>='*') return false;
		if (s[i]=='0' && s[i+1]=='0') return false;
		if (s[i]=='/' && s[i]=='0') return false;
		i++;
	}
	if (s[i-1]<'0' && s[i-2]<'0') return false;
	return true;
}

void work(string s)
{
	int i=0;
	while (s[i]!='@')
	{
		if (s[i]=='+' || s[i]=='-')
		{
			 while (!fuhao.empty() && fuhao.top()!='(')
			 {
				 x[t]=fuhao.top();
				 t++;
				 fuhao.pop();
			 }
			fuhao.push(s[i]);
			i++;
			continue;
		}
		
		if (s[i]=='*' || s[i]=='/')
		{
			 while (!fuhao.empty() && (fuhao.top()=='*' || fuhao.top()=='/'))
			 {
			 	 x[t]=fuhao.top();
				 t++;
				 fuhao.pop();
			 }
			 fuhao.push(s[i]);
			 i++;
			 continue;
		}
		
		if (s[i]=='(') 
		{
			fuhao.push(s[i]);
			i++;
			continue;
		}
		
		if (s[i]==')')
		{
			while (fuhao.top()!='(')
			{
				x[t]=fuhao.top();
				t++;
				fuhao.pop();
			}
			fuhao.pop();
			i++;
			continue;
		}
		
		else 
		{
			while(s[i]>='0' && s[i]<='9')
			{
				sz[r]=sz[r]*10+s[i]-'0';
				i++;
			}
			x[t]='0'+r;
			t++; r++;
		}
	}
	while (!fuhao.empty())
	{
		x[t]=fuhao.top();
		t++;
		fuhao.pop();
	}
}