#include <string.h>

size_t strspn(CONST char *s1, CONST char *s2)
	{
	int i;
	int j;

	for (i = 0; s1[i]; i++)
		{
		for (j = 0; s2[j]; j++)
			if (s1[i] == s2[j])
				break;
		if (s1[i] != s2[j])
			return i;
		}
	return i;
	}