#include<stdio.h>
#include<string.h>

int l,i;
char sir[105];

//   variabila/numar 1
//   paranteza [ 2, ] 3
//   BX/BP 4, SI/DI 5
//   +/- 6

inline bool lit(char &c)
{
    if(c>='a'&&c<='z')
        return 1;
    return 0;
}
inline bool cif(char &c)
{
    if(c>='0'&&c<='9')
        return 1;
    return 0;
}

inline int get_ch(int poz)
{
    if(sir[poz]=='B'||sir[poz]=='b')
        if(sir[poz+1]=='X'||sir[poz+1]=='x'||sir[poz+1]=='P'||sir[poz+1]=='p')
        {
            ++i;
            return 4;
        }

    if(sir[poz]=='S'||sir[poz]=='s'||sir[poz]=='D'||sir[poz]=='d')
        if(sir[poz+1]=='I'||sir[poz+1]=='i')
        {
            ++i;
            return 5;
        }

    if(lit(sir[poz])&&!lit(sir[poz+1]))return 1;
    if(cif(sir[poz])&& !cif(sir[poz+1]))return 1;
    if(sir[poz]=='[')return 2;
    if(sir[poz]==']')return 3;
    if(sir[poz]=='+'||sir[poz]=='-')return 6;



    return -1;
}

bool eval()
{
    int last=0,now,ap4=0,ap5=0,par=0,var=0;

    for(i=0;i<l;++i)
    {
        now=get_ch(i);
        if(now==-1)return 0;

        if(now==1)//variabila/numar 1
        {
            if(lit(sir[i]))++var;
            if(var>1)return 0;

            if(last==1||last==4||last==5)return 0;


        }else if(now==2)//   paranteza [ 2
        {
            ++par;


        }else if(now==3)//   paranteza ] 3
        {
            --par;
            if(par<0)return 0;
            if(last==6)return 0;
            //if(last==2)return 0;   ?

        }else if(now==6)//   +/- 6
        {
            if(last==0||last==2)return 0;


        }else if(now==4)//   BX/BP 4
        {
            ++ap4;
            if(ap4>1)return 0;
            if(last==1)return 0;

        }else if(now==5)//   SI/DI 5
        {
            ++ap5;
            if(ap5>1)return 0;
            if(last==1)return 0;

        }

        last=now;
    }


    if(last==6||par)return 0;



    return 1;
}

int main()
{
    //freopen("date.in","r",stdin);
    int ok;

    while(gets(sir))
    {
        l=strlen(sir);

        ok=eval();

        if(ok)
            printf("OK\n");
        else
            printf("ERROR\n");
    }

    return 0;
}