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

using namespace std;

int main(){
long m;
char x[200];
float cuv=0,lit=0;
ifstream f ("text.in");
ofstream o ("text.out");
 while (f>>x)
 f.getline(x,200);
 
 for(int i=0;i<strlen(x);i++)
 {if(x[i]==' ')
 cuv++;
 if(x[i]>='a' && x[i]<='z')
  lit++;}
 
 o<<abs(lit/cuv);
 




return 0;
}