#include <cstdio>
#include <cstring>
#include <set>

#define I_F "expression.in"
#define O_F "expression.out"

const int MAXl=2500;

char s[MAXl+1];
int ans;

void Input();
void Haha();
void Output();

int main()
{
	Input();
	Haha();
	Output();
	return 0;
}

void Input()
{
	freopen(I_F,"r",stdin);
	scanf("%s",s);
}

void Haha()
{
	std::set<char> se;
	se.clear();
	for (int i=0; i<strlen(s); ++i)
		if (se.find(s[i])==se.end())
			se.insert(s[i]);
	ans=se.size();
}

void Output()
{
	freopen(O_F,"w",stdout);
	printf("%d\n",ans);
}