var input = require("fs").readFileSync("input.txt").toString();
var replaced = input.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("");
console.log(replaced.length);