#pragma GCC optimize("O3")

#include <iostream>
#include <bitset>
#include <cstring>
#include <string>
#include <cassert>
#include <random>
#include <cmath>
#include <algorithm>
#include <map>
#include <unordered_map>
#include <queue>
#include <set>

namespace fastinput {
	/** Interface */

	template <class T = int> inline T readInt();
	inline long double readDouble();
	inline int readUInt();
	inline int readChar();
	inline void readWord(char *s);
	inline bool readLine(char *s); // do not save '\n'
	inline bool isEof();
	inline int peekChar();
	inline bool seekEof();

	template <class T> inline void writeInt(T x, int len = -1);
	template <class T> inline void writeUInt(T x, int len = -1);
	inline void writeChar(int x);
	inline void writeWord(const char *s);
	inline void writeDouble(long int x, int len = 0);
	inline void flush();

	/** Read */

	static const int buf_size = 4096;

	static char buf[buf_size];
	static int buf_len = 0, buf_pos = 0;

	inline bool isEof() {
		if (buf_pos == buf_len) {
			buf_pos = 0, buf_len = fread(buf, 1, buf_size, stdin);
			if (buf_pos == buf_len)
				return 1;
		}
		return 0;
	}

	inline int getChar() {
		return isEof() ? -1 : buf[buf_pos++];
	}

	inline int peekChar() {
		return isEof() ? -1 : buf[buf_pos];
	}

	inline bool seekEof() {
		int c;
		while ((c = peekChar()) != -1 && c <= 32)
			buf_pos++;
		return c == -1;
	}

	inline int readChar() {
		int c = getChar();
		while (c != -1 && c <= 32)
			c = getChar();
		return c;
	}

	inline int readUInt() {
		int c = readChar(), x = 0;
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		return x;
	}

	template <class T>
	inline T readInt() {
		int s = 1, c = readChar();
		T x = 0;
		if (c == '-')
			s = -1, c = getChar();
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		return s == 1 ? x : -x;
	}

	inline long double readDouble() {
		int s = 1, c = readChar();
		long double x = 0;
		if (c == '-')
			s = -1, c = getChar();
		while ('0' <= c && c <= '9')
			x = x * 10 + c - '0', c = getChar();
		if (c == '.') {
			c = getChar();
			long double coef = 1;
			while ('0' <= c && c <= '9')
				x += (c - '0') * (coef *= 0.1), c = getChar();
		}
		return s == 1 ? x : -x;
	}

	inline void readWord(char *s) {
		int c = readChar();
		while (c > 32)
			*s++ = (char)c, c = getChar();
		*s = 0;
	}

	inline bool readLine(char *s) {
		int c = getChar();
		while (c != '\n' && c != -1)
			*s++ = (char)c, c = getChar();
		*s = 0;
		return c != -1;
	}

	/** Write */

	static int write_buf_pos = 0;
	static char write_buf[buf_size];

	inline void writeChar(int x) {
		if (write_buf_pos == buf_size)
			fwrite(write_buf, 1, buf_size, stdout), write_buf_pos = 0;
		write_buf[write_buf_pos++] = (char)x;
	}

	inline void flush() {
		if (write_buf_pos)
			fwrite(write_buf, 1, write_buf_pos, stdout), write_buf_pos = 0;
	}

	template <class T>
	inline void writeInt(T x, int output_len) {
if (x < 0)
	writeChar('-'), x = -x;

char s[24];
int n = 0;
while (x || !n)
s[n++] = (char)('0' + (char)(x % 10)), x /= 10;
while (n < output_len)
	s[n++] = '0';
while (n--)
writeChar(s[n]);
	}

	template <class T>
	inline void writeUInt(T x, int output_len) {
		char s[24];
		int n = 0;
		while (x || !n)
			s[n++] = (char)('0' + (char)(x % 10)), x /= 10;
		while (n < output_len)
			s[n++] = '0';
		while (n--)
			writeChar(s[n]);
	}

	inline void writeWord(const char *s) {
		while (*s)
			writeChar(*s++);
	}

	inline void writeDouble(long int x, int output_len) {
		if (x < 0)
			writeChar('-'), x = -x;
		int t = (int)x;
		writeUInt(t), x -= t;
		writeChar('.');
		for (int i = output_len - 1; i > 0; i--) {
			x *= 10;
			t = std::min(9, (int)x);
			writeChar('0' + t), x -= t;
		}
		x *= 10;
		t = std::min(9, (int)(x + 0.5));
		writeChar('0' + t);
	}
}

using namespace fastinput;
using namespace std;

///** Begin fast allocation */
//const int MAX_MEM = 64e6;
//int mpos = 0;
//char mem[MAX_MEM];
//inline void * operator new (size_t n) {
//  mpos += n;
//  return (void *)(mem + mpos - n);
//}
//inline void operator delete (void *) noexcept {} // must have!
//                                               /** End fast allocation */

const int N = 2e5 + 10;
const int ANTIBADTEST = 1000;
const int ALPHABET = 26;
int masked[1 << ALPHABET];
int masks[N];
int dp[N];

int popcnt(int x) {
	int keep = 0;
	while (x) {
		x = x & (x - 1);
		++keep;
	}
	return keep;
}

int answerFast(string s) {
	int n = s.length();
	int curmask = 0;
	memset(masked, -1, sizeof(masked));
	masks[0] = 0;
	masked[0] = 0;
	map<char, int> mp;
	for (int i = 0; i < n; ++i) {
		mp[s[i]] = 1;
	}
	for (int i = 0; i <= n; ++i)
		dp[i] = i;
	for (int i = 0; i < n; ++i) {
		curmask ^= 1 << (s[i] - 'a');
		for (int j = 0; j < ALPHABET; ++j) {
			int shifted = curmask ^ (1 << j); //there MUST always be singular letter, otherwise merge.
			if (masked[shifted] != -1) {
				int go = masked[shifted];
				dp[i + 1] = min(dp[i + 1], dp[go] + 1);
			}
		}
		masks[i + 1] = curmask;
		masked[curmask] = i + 1;
	}
	for (int i = 0; i < n; ++i)
		dp[i + 1] = min(dp[i + 1], dp[i] + 1);
	if (popcnt(masks[n]) <= 1) {
		return 1;
	}
	for (int i = 0; i < n; ++i) {
		int pr = masks[i];
		int go = -1;
		for (int j = 0; j < ALPHABET; ++j) {
			int shifted = pr ^ (1 << j); //there MUST always be singular letter, otherwise merge.
			if (masked[shifted] != -1) {
				int go = masked[shifted];
				dp[go] = min(dp[go], dp[i] + 1);
			}
		}
		for (int shifter = 0; shifter < ANTIBADTEST && i + shifter <= n; ++shifter) {
			if (popcnt(masks[i + shifter] ^ pr) <= 1) {
				dp[i + shifter] = min(dp[i + shifter], dp[i] + 1);
			}
		}
	}
	return dp[n];
}

int main() {
	string s;
	cin >> s;
	cout << answerFast(s) << endl;
	return 0;
}

Measured memory_bytes: 264452