#include <bits/stdc++.h>
using namespace std;
const long long inf = 2147383647;
const double pi = 2 * acos(0.0);
const double eps = 1e-9;
inline long long gcd(long long a, long long b) {
  a = ((a) < 0 ? -(a) : (a));
  b = ((b) < 0 ? -(b) : (b));
  while (b) {
    a = a % b;
    swap(a, b);
  }
  return a;
}
long long ext_gcd(long long A, long long B, long long *X, long long *Y) {
  long long x2, y2, x1, y1, x, y, r2, r1, q, r;
  x2 = 1;
  y2 = 0;
  x1 = 0;
  y1 = 1;
  for (r2 = A, r1 = B; r1 != 0;
       r2 = r1, r1 = r, x2 = x1, y2 = y1, x1 = x, y1 = y) {
    q = r2 / r1;
    r = r2 % r1;
    x = x2 - (q * x1);
    y = y2 - (q * y1);
  }
  *X = x2;
  *Y = y2;
  return r2;
}
inline long long modInv(long long a, long long m) {
  long long x, y;
  ext_gcd(a, m, &x, &y);
  x %= m;
  if (x < 0) x += m;
  return x;
}
inline long long power(long long a, long long p) {
  long long res = 1, x = a;
  while (p) {
    if (p & 1) res = (res * x);
    x = (x * x);
    p >>= 1;
  }
  return res;
}
inline long long bigmod(long long a, long long p, long long m) {
  long long res = 1 % m, x = a % m;
  while (p) {
    if (p & 1) res = (res * x) % m;
    x = (x * x) % m;
    p >>= 1;
  }
  return res;
}
int freq[150];
int main() {
  string s;
  cin >> s;
  int siz = s.size();
  for (int i = 0; i < siz; i++) {
    freq[s[i]]++;
  }
  int mn = siz;
  mn = ((mn) < (freq['B']) ? (mn) : (freq['B']));
  mn = ((mn) < (freq['u'] / 2) ? (mn) : (freq['u'] / 2));
  mn = ((mn) < (freq['l']) ? (mn) : (freq['l']));
  mn = ((mn) < (freq['b']) ? (mn) : (freq['b']));
  mn = ((mn) < (freq['s']) ? (mn) : (freq['s']));
  mn = ((mn) < (freq['a'] / 2) ? (mn) : (freq['a'] / 2));
  mn = ((mn) < (freq['r']) ? (mn) : (freq['r']));
  cout << mn << endl;
}
