#include<bits/stdc++.h>
using namespace std;
int main() {
    string S;
    cin>>S;
    int B=0,u=0,l=0,b=0,a=0,s=0,r=0,count=0,n=1;
    int ln=S.size();
    for(int i=0; i<ln; i++) {
        if(S[i]=='B') B++;
        else if(S[i]=='u') u++;
        else if(S[i]=='l') l++;
        else if(S[i]=='b') b++;
        else if(S[i]=='s') s++;
        else if(S[i]=='a') a++;
        else if(S[i]=='r') r++;
        if(B>=n&&b>=n*2&&u>=n*2&&a>=n*2&&l>=n&&s>=n&&r>=n) {
            count++;
            n++;
        }
    }
    cout<<count<<endl;
    return 0;
}