#include <iostream>
#include <string.h>

using namespace std;

int main()
{
   char line[101];
   cin.get(line,100);
   cin.get();
   while(line[0]!=NULL){

        int ok=1,br=0,ir=0,o=0,c=0,v=0;

        for(int i=0;i<strlen(line) && ok;i++){
            if(line[i]=='[')
                {o++;

                }
            else if (line[i]==']')
                {c++;
                }
            else if ((line[i]=='b' || line[i]=='B') && (line[i+1]=='x' || line[i+1]=='X' || line[i+1]=='p' || line[i+1]=='P') && i+1<strlen(line))
                {br++;i++;
                }
             else if ((((line[i]=='s' || line[i]=='S') && (line[i+1]=='i' || line[i+1]=='I')) || ((line[i]=='d' || line[i]=='D') && (line[i+1]=='i' || line[i+1]=='I')))&& i+1<strlen(line))
                {ir++;i++;
                }
            else if (line[i]>='a' && line[i]<='z')
                {v++;}
            else if(line[i]=='[')
                {o++;
                }
            else if(line[i]==']')
                {c++;
                }
            else if((line[i]=='+' || line[i]=='-')  &&( (line[i-1]=='[' && i-1>=0) || (i+1<strlen(line) &&line[i+1]==']')) || i==0 || i==strlen(line))
               { ok=0;
               }
            else if (line[i]!='+' && line[i]!='-' && (line[i]<'0' || line[i]>'9'))
               { ok=0;}
            if (br>1 || ir>1 ||v>1 || c>o)
                ok=0;
        }
        if(ok && c==o)  cout<<"OK"<<endl;
        else cout<<"ERROR"<<endl;
        cin.getline(line,100);

   }
}