#include <iostream>
#include <map>
#include <vector>
#include <algorithm>
#include <cctype>
#include <set>
#include <fstream>
#include<string>

using namespace std;

ifstream in("text.in");
ofstream out("text.out");

void readData(string &s) {	
	getline(in, s);
}
double WordLettersAvg(string s)
{
	int letters = 0, words = 0, inWord = 0;
	for (char c : s) {

		if (((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) && inWord == 1) {
			letters++;
		}

		if (((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) && inWord==0) {
			words++;
			letters++;
			inWord = 1;
		}
	
		if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')))
		{
			inWord = 0;
		}
	}
	return letters / words;
}
int main()
{
	string s;
	readData(s);
	out << WordLettersAvg(s);
	in.close();
	out.close();
	return 0;
}