#include <bits/stdc++.h>
using namespace std;
bool debug = false;
int n, m, k;
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
long long ln, lk, lm;
char s[1000005];
vector<int> mp[1000005];
int ans;
bool vis[1000005];
int dfs(int x) {
  int y = 1;
  if (mp[x].size() == 1) y += dfs(mp[x][0]);
  return y;
}
void col(int x) {
  vis[x] = 1;
  for (int c : mp[x]) col(c);
}
void wk(int i, int tar) {
  vis[tar] = 1;
  ans++;
  int o = (tar + 1) % n;
  if (o == i) o = (tar - 1 + n) % n;
  if (!vis[o]) {
    vis[o] = 1;
    int oo = mp[o][0];
    if (oo == tar) oo = mp[o][1];
    if (!vis[oo]) wk(o, oo);
  }
}
int main() {
  scanf("%s", s);
  n = strlen(s);
  for (int(i) = 0; (i) < (int)(n); (i)++) {
    if (s[i] == '0')
      mp[i].push_back((i + 1) % n);
    else
      mp[(i + 1) % n].push_back(i);
  }
  for (int(i) = 0; (i) < (int)(n); (i)++)
    if (mp[i].size() == 2) {
      int y = dfs(mp[i][0]);
      if (y > 1) {
        ans++;
        col(mp[i][0]);
        vis[i] = 1;
      }
      y = dfs(mp[i][1]);
      if (y > 1) {
        ans++;
        vis[i] = 1;
        col(mp[i][1]);
      }
    }
  for (int(i) = 0; (i) < (int)(n); (i)++)
    if (vis[i] && mp[i].size() == 2) {
      int tar = -1;
      if (!vis[mp[i][0]]) tar = mp[i][0];
      if (!vis[mp[i][1]]) tar = mp[i][1];
      if (tar == -1) continue;
      wk(i, tar);
    }
  for (int(i) = 0; (i) < (int)(n); (i)++)
    if (!vis[i] && mp[i].size() == 2) ans++;
  printf("%d\n", ans);
  return 0;
}
