#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    int n,i,ss,nr,aux;
    float ma;
    string s;
    ss=0;
    nr=0;
    ifstream f("text.in");
    ofstream g("text.out");
    getline(f,s);
    n=s.size();
    for (i=0;i<n;i++)
    {
        if ((s[i]>='a'&&s[i]<='z')||(s[i]>='A'&&s[i]<='Z'))
            {
                ss=ss+1;
                aux=1;
            }
        else if (aux==1)
            {
                  nr=nr+1;
                  aux=0;
            }
    }
    if (aux==1)
        nr=nr+1;
    ma=(float)ss/nr;
    g<<ma;
    return 0;
}