C++ :

#include<iostream>
#include<string>
#include<cctype>
using namespace std;
int main()
{
	string s;
	getline(cin,s);
	int len=s.size(),ans=0;
	for (int i=0; i<len; i++)
		if (isalpha(s[i])) ans++;
	cout<<ans<<endl;
	return 0;
}