var input = require("fs").readFileSync("input.txt").toString().replace("\n", "");
replace = str=>(str.split("").filter(a=>(a!="\n")).reduce((a,b)=>{
	var c = a.pop();
	if(c){
		if(!((b!=c) && (b.toLowerCase()==c.toLowerCase()))){
			a.push(c);
			a.push(b);
		}
	}
	else{
		a.push(b);
	}
	return a;
}, []).join(""));

var strs = [];
for(var i = 0; i < 26; i++){
	strs.push(input.split("").filter((a)=>(a.toLowerCase().charCodeAt(0) != (97 + i))).join(""));
}
var lengths = strs.map(a=>(replace(a))).map(a=>(a.length));
console.log(Math.min.apply(null, lengths));