What does this C snippet output?

1#include <stdio.h>
2int main(void) {
3    char s[] = "abcABC";
4    int diff = 0;
5    for (int i = 0; s[i]; i++)
6        if (s[i] >= 'a' && s[i] <= 'z') diff++;
7    printf("%d\n", diff);
8    return 0;
9}