
#include <stdio.h>
#include <ctype.h>
#include <string.h>


int main() {
	int N;
	
	scanf("%d", &N);
	int i,j;
	int a[200001] = { 0 };
	int sum = 0;
	for (i = 1; i < N+1; i++) {
		char s;
		scanf("%s", &s);
		j = 0;
		for (j; j < i; j++) {
			if (j!=i&&s == a[j]) {
				j = i;
			}
			else if (j==i-1){
				a[i] = s;
				sum += 1;
			}
		}
	}
	printf("%d", sum);
	return 0;
}