#include <bits/stdc++.h>
using namespace std;
long long power(long long base, long long pow, long long mo) {
  long long res = 1;
  while (pow) {
    if (pow % 2 != 0) res = (res * base) % mo;
    base = (base * base) % mo;
    pow /= 2;
  }
  return res;
}
long long inv(long long i) { return power(i, 1000000007 - 2, 1000000007); }
std::string str = "All Good Till Here";
void solve() {
  long long i, j, x, n;
  string str;
  cin >> str;
  long long up = 0, lr = 0, up1 = 0, lr1 = 0;
  n = str.length();
  for (long long i = 0; i < n; i++) {
    if (str[i] >= 'a' && str[i] <= 'z')
      lr++;
    else
      up++;
  }
  long long ans = INT_MAX;
  for (long long i = 0; i < n; i++) {
    ans = min(ans, lr1 + up - up1);
    if (str[i] >= 'a' && str[i] <= 'z')
      lr1++;
    else
      up1++;
  }
  ans = min(ans, lr1 + up - up1);
  cout << ans << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long tt;
  tt = 1;
  while (tt--) {
    solve();
  }
  return 0;
}
