# include <fstream>
# include <string.h>

using namespace std;

int main ()
{
    char t[1001];
    unsigned lit=0,cuv=0;
    ifstream fin ("text.in");
    ofstream fout("text.out");

    while(fin.get(t,1001))
    {
        for(int i = 0; i < strlen(t); i++)
       {if((t[i] >= 'a' && t[i]<='z')||(t[i]>='A'&&t[i]<='Z'))
        lit++;
            if(t[i+1]>=' '&& t[i+1]<='@'&& (t[i] >= 'a' && t[i]<='z'))
        cuv++;

        else
       {if(t[i]>=' '&& t[i]<='@'&& (t[i] >= 'a' && t[i]<='z'))
        cuv++;
        }}

    }
    if(cuv==0)
    fout<<0;
 else
   fout<<lit/cuv;
   fin.close();
   fout.close();
    return 0;
}