#include <stdio.h>
#include <string.h>

int collapse(char *in, char *out, char skip) {
	#define CASE_BIT ('A' ^ 'a')
	int c;
	char *end = out - 1;
	while (c = *in++) {
		if ((c ^ skip) & ~CASE_BIT) {
			if (end >= out && (c ^ CASE_BIT) == *end) --end;
			else *++end = c;
		}
	}
	*++end = '\0';
	return end - out;
}

int main(int argc, char *argv[]) {
	#define IO_ERROR 2
	#define INPUT_TOO_LONG 1
	#define SUCCESS 0
	#define MAX_LENGTH 65536
	static char polymer[MAX_LENGTH], collapsed[MAX_LENGTH];
	int length, shortest, skip, status = IO_ERROR;
	FILE *input;
	if (input = fopen("input.txt", "r")) {
		if (fgets(polymer, MAX_LENGTH, input)) {
			status = INPUT_TOO_LONG;
			length = strlen(polymer) - 1;
			if (length >= 0 && polymer[length] == '\n') {
				status = SUCCESS;
				polymer[length] = '\0';
				shortest = length;
				for (skip = 'a'; skip <= 'z'; ++skip) {
					length = collapse(polymer, collapsed, skip);
					if (shortest > length) shortest = length;
				}
				printf("%d\n", shortest);
			}
		}
		fclose(input);
	}
	return status;
}