求教大佬

#include<bits/stdc++.h>
using namespace std;
#define int long long
queue<int>t;
signed main(){
//	freopen("123456789.in","r",stdin);
	//freopen(".out","w",stdout);
	//ios::sync_with_stdio(false);
	//cin.tie(0);
	//cout.tie(0);
	//srand(time(NULL));
	string ss;
	getline(cin,ss);
	int ans=0;
	int s=1;
	for(int i=0;i<ss.size();i++){
		char a=ss[i];
		if(a=='R'){
			i+=7;
			int j=i;
			if(j>=ss.size()) break;
			int x=0;
			while(isdigit(ss[j])){
				if(j>=ss.size()) break;
				x=x*10+ss[j]-'0';
				j++;
			}
			i=j;
			t.push(x);
			s*=x;
		}
		else if(a=='B'){
			i+=3;
			int x=0,j=i;
			if(j>=ss.size()) break;
			while(isdigit(ss[j])){
				if(j>=ss.size()) break;
				x=x*10+ss[j]-'0';
				j++;
			}
			ans-=s*x;
		}
		else if(a=='F'){
			i+=3;
			int x=0,j=i;
			if(j>=ss.size()) break;
			while(isdigit(ss[j])){
				if(j>=ss.size()) break;
				x=x*10+ss[j]-'0';
				j++;
			}
			ans+=s*x;
		}
		else if(a==']'){
			s/=t.front();
			t.pop();
		}
	}
	cout<<abs(ans);
	return 0;
}

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