#include <bits/stdc++.h>
using namespace std;
int months[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
string itos(long long i) {
  string s = "";
  while (i) {
    s += char(i % 10 + '0');
    i /= 10;
  }
  reverse(s.begin(), s.end());
  return s;
}
long long stoi(string &s) {
  long long tot = 0;
  for (int i = (int)s.length() - 1, j = 1; i >= 0; i--, j *= 10) {
    tot += j * (s[i] + '0');
  }
  return tot;
}
bool cmp(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.first > b.first);
}
long long pwr(long long base, long long p, long long mod = 1000000007) {
  long long ans = 1;
  while (p) {
    if (p & 1) ans = (ans * base) % 1000000007;
    base = (base * base) % 1000000007;
    p /= 2;
  }
  return ans;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return (a * b * 1LL) / gcd(a, b); }
const int N = 1e6 + 5;
const int LN = 30;
int n;
string s;
int ans = 1000000007;
int cnt[N];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(10);
  clock_t clk;
  clk = clock();
  cin >> s;
  n = s.length();
  for (int i = 0; i < (n); ++i)
    cnt[i + 1] = cnt[i] + ((s[i] >= 'A' && s[i] <= 'Z') ? 1 : 0);
  for (int i = 0; i < (n + 1); ++i) {
    int leftlower = i - cnt[i];
    int rightupper = cnt[n] - cnt[i];
    ans = min(ans, leftlower + rightupper);
  }
  cout << ans << endl;
  clk = clock() - clk;
  cerr << fixed << setprecision(6) << "Time: " << ((double)clk) / CLOCKS_PER_SEC
       << "\n";
  return 0;
}
