#include <iostream>
#include <fstream>
using namespace std;
ifstream fi("text.in");
ofstream fo("text.out");
string s;
unsigned int sum,k,i;

int main()
{
    sum=0;k=0;
    while(!fi.eof())
    {
         ret:
         if(fi.eof()) goto en;
         fi>>s;
         if(s.length()<2) goto ret;
         
         for(i=0;i<s.length();i++)
         {if((!((int)s[i]>=96) && ((int)s[i]<=122)) && (!((int)s[i]>=65) && ((int)s[i]<=90))) goto ret;}
         
         sum+=s.length();
         k++;
    }
    en:
    if(k!=0)fo<<sum/k;
    fi.close();
    fo.close();
}