#include <fstream>
using namespace std;

int main()
{
    int n,i,ss,nr,aux;
    float ma;
    char s;
    ss=0;
    nr=0;
    aux=0;
    ifstream cin("text.in");
    ofstream cout("text.out");
    while (cin.get(s))
    {
        if (((s>='a')&&(s<='z'))||((s>='A')&&(s<='Z')))
            {
                ss=ss+1;
                aux=1;
            }
        else if (aux==1)
            {
                  nr=nr+1;
                  aux=0;
            }
    }
    if (aux==1)
        nr=nr+1;
    ma=ss/nr;
    cout<<ma;
    return 0;
}