#include <cstdio>
#include <cstring>

using namespace std;

char sir[100005];

int valid(char &c){
  if(c == '+' || c == '-' || c == '[' || c == ']' || (c >= '0' && c <= '9') || (c >= 'a' && c <= 'z'))
    return 1;
  if(c == 'B' || c == 'D' || c == 'P' || c == 'S' || c == 'X' || c == 'I'){
    c -= 'A';
    c += 'a';
    return 1;
  }
  return 0;
}

int p, lim;
int kkt1 = 0, kkt2 = 0, kkt = 0;

int lit(int x){
  return (sir[x] >= 'a' && sir[x] <= 'z');
}

int lel(int pos){
  if(sir[pos] == 'B')
    return (sir[pos + 1] == 'x' || sir[pos + 1] == 'X' || sir[pos + 1] == 'P' || sir[pos + 1] == 'p');
  if(sir[pos] == 'D' || sir[pos] == 'S')
    return sir[pos + 1] == 'I' || sir[pos + 1] == 'i';
  if(sir[pos] == 'I')
    return sir[pos - 1] == 'D' || sir[pos - 1] == 'd' || sir[pos - 1] == 's' || sir[pos - 1] == 'S';
  if(sir[pos] == 'X' || sir[pos] == 'P')
    return sir[pos - 1] == 'B' || sir[pos - 1] == 'b';
  return 1;
}

int cauta_inadvertente(){
  for(int i = p; i < lim; ++i)
    if(!lel(i))
      return 0;
  for(int i = p; i < lim; ++i)
    if(!valid(sir[i]))
      return 0;

  kkt1 = kkt2 = kkt = 0;
  for(int i = 0; i < lim; ++i)
    if(lit(i) && !lit(i + 1))
      ++kkt;
    else if(lit(i)){
      if(sir[i] == 'b'){
        ++kkt1;
        sir[i + 1] = '0';
      }
      else if(sir[i] == 'd' || sir[i] == 's'){
        ++kkt2;
        sir[i + 1] = '0';
      }
      else
        return 0;
    }
  if(kkt1 > 1 || kkt2 > 1 || kkt > 1)
    return 0;

  if(sir[0] == ']' || sir[lim - 1] == '[' || sir[0] == '+' || sir[0] == '-' || sir[lim - 1] == '+' || sir[lim - 1] == '-')
    return 0;
  int numd = 0;
  for(int i = 0; i < lim; ++i)
    if(sir[i] == '['){
      ++numd;
      if(sir[i + 1] == '+' || sir[i + 1] == '-' || sir[i + 1] == ']')
        return 0;
    }
    else if(sir[i] == ']'){
      --numd;
      if(numd < 0)
        return 0;
      if(sir[i - 1] == '+' || sir[i - 1] == '-')
        return 0;
    }

  return 1;
}

int main(){
  #ifndef ONLINE_JUDGE
    freopen("kek.in", "r", stdin);
  #endif

  while(gets(sir)){
    p = 0;
    lim = strlen(sir);
    if(cauta_inadvertente())
      printf("OK\n");
    else
      printf("ERROR\n");
  }

  return 0;
}