萌新求助QAQ

/*(^-^)*/
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<cmath>
#include<ctime>
#include<cstdio>
#include<vector>
#include<cctype>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define ll long long
ll w,p[105],t;
string s,m,x;

int main()
{	
	cin>>s;
	ll l=s.length();
	for(ll i=0;i<l;i++)
    	if(s[i]=='[')
    		p[++t]=i;
	for(ll i=t;i;i--)
	{
		ll j=p[i]+1,a=0,len=2;
		m.clear();
		x.clear();
		//while(s[j]!=']')
		for(ll j=p[i]+1;s[j]!=']';j++)
		{
			if(s[j]>='0'&&s[j]<='9')a=a*10+s[j]-'0';
			else m+=s[j];
			//j++;
			len++;
		}
		for(ll j=1;j<=a;j++)x+=m;
		s.erase(p[i],len);
		s.insert(p[i],x);
	}
	cout<<s<<endl;
	return 0;
}
//P1928