import java.util.*;
class DecodeString{
private String decodeString(String s){
Deque st= new ArrayDeque<>();
for(char c: s.toCharArray())
st.offer(c);
return decode(st);
}
private String decode(Deque st){
StringBuilder sb= new StringBuilder();
int num=0;
while(!st.isEmpty()){
char c= st.poll();
if(Character.isDigit(c)){
num = num * 10 + c - '0';
}
else if(c == '['){
String substr= decode(st);
for(int i=0; i