#include <fstream>
#include <cstring>

using namespace std;
char s[10000000001],*p;
ifstream f("text.in");
ofstream g("text.out");
long long nrcuv,lit;
int main()
{
    while(f.getline(s,10000000001))
    {
       p=strtok(s," -;,:?!");
       while(p)
       {
           nrcuv++;
           for(int i=0;i<strlen(p);i++)
             if((p[i]>='a' && p[i]<='z') || (p[i]>='A' &&p[i]<='Z'))
                 lit++;
           p=strtok(NULL," -;,:?!");
       }
    }
    g<<lit/nrcuv;
    f.close();g.close();
    return 0;
}