```go
package main

import (
	"bufio"
	"fmt"
	"os"
	"unicode"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	s := scanner.Text()
	n := len(s)
	prefixL := make([]int, n+1)
	prefixL[0] = 0
	for i := 1; i <= n; i++ {
		if unicode.IsLower(rune(s[i-1])) {
			prefixL[i] = prefixL[i-1] + 1
		} else {
			prefixL[i] = prefixL[i-1]
		}
	}
	totalL := prefixL[n]
	minCost := n + 1
	for k := 0; k <= n; k++ {
		cost := 2*prefixL[k] + n - k - totalL
		if cost < minCost {
			minCost = cost
		}
	}
	fmt.Println(minCost)
}
```