import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static string[] s_rd;
T RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
string RDR()() { return readln.chomp; }
T[] ARR(T = long)(in string str, T fix = 0) { auto r = str.split.to!(T[]); r[] += fix; return r; }
size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
long lcm(long x, long y) { return x * y / gcd(x, y); }

long mod = 10^^9 + 7;
//long mod = 998244353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }

void main()
{
	auto s = RD!string;
	long ans;
	auto cnt = new long[](26);
	foreach (i; 0..26)
	{
		auto tokens = s.split(['a'+i]);
		long len;
		foreach (token; tokens)
		{
			len = max(len, token.length);
		}
		cnt[i] = len;
	}
	char c = cast(char)('a' + MIN_POS(cnt));
	while (true)
	{
		bool ok = true;
		foreach (cc; s)
		{
			if (cc != c)
			{
				ok = false;
				break;
			}
		}
		if (ok) break;
		++ans;
		string ns;
		auto streaks = new long[](s.length);
		long streak;
		foreach (i; 0..s.length-1)
		{
			if (s[i] == c || s[i+1] == c)
			{
				ns ~= c;
				streaks[i] = streak;
				streak = 0;
			}
			else
			{
				ns ~= s[i];
				++streak;
			}
		}
		/*if (s[$-1] == c)
		{
			ns ~= c;
			long pos = MIN_POS!"a > b"(streaks);
			long mid = max(pos-1,0);
			s = ns[0..mid] ~ ns[mid+1..$];
		}
		else*/
		{
			s = ns;
		}
		debug writeln(s);
	}

	writeln(ans);
	stdout.flush();
	debug readln();
}
