#include <bits/stdc++.h>
using namespace std;
 
int main() {
	// your code goes here
	string a;
	cin>>a;
	int n=a.size();
	vector<int>arr(n,0);
	unordered_map<int,int>pre;     //hashmap contains prefix sum and index
	pre[0]=-1;
	for(int i=0;i<n;i++){
		if(a[i]=='a'){
			arr[i]=1;
		}
		else{
			arr[i]=-1;
		}
	}
	int mini=1e9;
	int sum=0;
	for(int i=0;i<n;i++){
		sum+=arr[i];
		if(pre.find(sum)!=pre.end()){
			int len=i-pre[sum];
			mini=min(len,mini);
 
		}
		pre[sum]=i;
	}
	cout<<"The minimum subarray that must be removed to get the array with equal count of a and b is:"<<mini;
	return 0;
}

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