include<bits/stdc++.h>

using namespace std; string str; int ans=INT_MAX,a[15]; int main(){

cin>>str;
for(int i=0;i<str.size();i++){
	if(str[i]=='B') a[1]++;
	else if(str[i]=='u') a[2]++;
	else if(str[i]=='l') a[3]++;
	else if(str[i]=='b') a[4]++;
	else if(str[i]=='a') a[5]++;
	else if(str[i]=='s') a[6]++;
	else if(str[i]=='r') a[7]++;
}
for(int i=1;i<=7;i++){
	if(i==1) ans=min(ans,a[i]/1);
	else if(i==2) ans=min(ans,a[i]/2);
	else if(i==3) ans=min(ans,a[i]/1);
	else if(i==4) ans=min(ans,a[i]/1);
	else if(i==5) ans=min(ans,a[i]/2);
	else if(i==6) ans=min(ans,a[i]/1);
	else if(i==7) ans=min(ans,a[i]/1);
}
cout<<ans;
return 0;

}