#include <iostream>
#include <fstream>

using namespace std;
ifstream f("text.in");
ofstream g("text.out");
int main()
{
    int s=0,c=0,n,s1=s;
    while (f>>n) {
        f>>n;
        for (char i='a';i<='z';i++) if (i==n) s++;
        for (char i='A';i<='Z';i++) if (i==n) s++;
        if (s1==s) c++;
        s1=s;
    }
    g<<(int)s/c;
}