#include<bits/stdc++.h>
using namespace std;
int l,i,j,len,ans;
char s[102],s1[102],s2[102],c;
bool fl;
int main(){
	scanf("%s",s),l=strlen(s);
	ans=1e9;
	for (c='a';c<='z';c++){
		memcpy(s2,s,sizeof(s));
		len=l;
		for (j=0;;j++){
			fl=1;
			for (i=0;i<len && fl;i++)
				if (s2[i]!=c) fl=0;
			if (fl) break;
			swap(s1,s2);
			for (i=0;i<len-1;i++)
				if (s1[i]==c || s1[i+1]==c) s2[i]=c;
				else s2[i]=s1[i];
			len--;
		}
		ans=min(ans,j);
	}
	printf("%d",ans);
}