/* -*- coding: utf-8 -*-
 *
 * 1924.cc:  No.1924 3 color painting on a line - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d%s", &n, s);

  int m = 0;
  for (int i = 0; i < n;) {
    int j = i;
    while (i < n && s[j] == s[i]) i++;
    s[m++] = s[j];
  }
  s[m] = '\0';
  n = m;
  //puts(s);

  int c = 0;
  m = 0;
  for (int i = 0; i < n; i++) {
    if (m >= 2 && s[m - 2] == s[i]) m -= 2, c++;
    s[m++] = s[i];
  }
  s[m] = '\0';
  n = m;
  //printf("%s, c=%d\n", s, c);

  for (int i = 0; i < n; i++)
    if (i % 3 != 0) s[i] = '\0', c++;
  //printf("%s, c=%d\n", s, c);

  printf("%d\n", c + 1);
  return 0;
}