#include #include #include #include #include #include #include #include using namespace std; #define REP(i,n) for(int i=0;i<(n);++i) #define REPS(i,s,t) for(int i=(s);i<(t);++i) #define INF 2000000007 #define MOD 1000000007 #define MAX 200005 typedef unsigned int uint; typedef unsigned long long int ull; typedef long long int ll; //int dp[MAX]; pair dp[MAX]; int main(){ string str;cin>>str; int len = str.size(); dp[0].first=0;dp[0].second=0; REPS(i,1,len+1){ dp[i].first = dp[i-1].first + (str[i-1]=='A' ? 1 : -1); dp[i].second = i; } sort(dp,dp+len+1); int maxl = 0; REP(i,len+1){ auto st = dp[i]; while(st.first == dp[++i].first) if(i>len)break; maxl = max(maxl,dp[--i].second - st.second); } cout << maxl << endl; return 0; }