#include <bits/stdc++.h>
using namespace std;
int main() {
// your code goes here
string a;
cin>>a; //string consisting of only a and b
int totalA=0;
int totalB=0;
int n=a.size();
for(int i=0;i<n;i++){
if(a[i]=='a'){
totalA++;
}
else{
totalB++;
}
}
int mini=1e9;
for(int i=0;i<n;i++){
int countA=0;
int countB=0;
for(int j=i;j<n;j++){
if(a[j]=='a'){
countA++;
}
else{
countB++;
}
int Ca=totalA-countA; //total count of a after removing from substring
int Cb=totalB-countB;
if(Ca==Cb){
int len=j-i+1;
mini=min(mini,len);
}
}
}
cout<<"The minimum substring containing equal number of a and b is:"<<mini;
return 0;
}
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