#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>



int main(int argc, char *argv[])
{

	int N = 0;
	scanf("%d", &N);

	char A[100] = "";

	for (int j = 0; j < N; j++)
	{
		scanf("%c", &A[j]);
	}


	int lSum = 0;
	for (int i = 0; i < (N - 2); i++)
	{
		if (A[i] < A[i + 1] &&
			A[i + 2] < A[i + 1])
			lSum++;
	}
	printf("%d\n", lSum);

	return 0;

}