#include <bits/stdc++.h>
const long long MOD1 = 1000000007;
const long long MOD2 = 998244353;
#define logn long
#define lnog long
#define itn int
using namespace std;
int main() {
	long long N; cin >> N;
	string T; cin >> T;
	for (long long i = 1; i < N; i++) {
		if (T.at(i - 1) == '0' && T.at(i) == '0') {
			cout << 0 << endl;
			return 0;
		}
	}
	for (long long i = 1; i < N - 1; i++) {
		if (T.at(i - 1) == '0' && T.at(i) == '1' && T.at(i + 1) == '0') {
			cout << 0 << endl;
			return 0;
		}
		else if (T.at(i - 1) == '1' && T.at(i) == '1' && T.at(i + 1) == '1') {
			cout << 0 << endl;
			return 0;
		}
	}
	long long num = 0;
	for (long long i = 0; i < N; i++) {
		num += (T.at(i) == '0');
	}
	if (T == "1") {
		cout << 2 * 10000000000 << endl;
	}
	else if (T == "11") {
		cout << 10000000000 << endl;
	}
	else {
		cout << 10000000000 - num + (T.at(N - 1) == '0') << endl;
	}
}
#include <bits/stdc++.h>
using namespace std;

#define INF_LL (int64)1e18
#define INF (int32)1e9
#define REP(i, n) for(int64 i = 0;i < (n);i++)
#define FOR(i, a, b) for(int64 i = (a);i < (b);i++)
#define all(x) x.begin(),x.end()
#define fs first
#define sc second

using int32 = int_fast32_t;
using uint32 = uint_fast32_t;
using int64 = int_fast64_t;
using uint64 = uint_fast64_t;
using PII = pair<int32, int32>;
using PLL = pair<int64, int64>;

const double eps = 1e-10;

template<typename A, typename B>inline void chmin(A &a, B b){if(a > b) a = b;}
template<typename A, typename B>inline void chmax(A &a, B b){if(a < b) a = b;}

template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
	return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value!=0>::type
fill_v(U &u,const V... v){u=U(v...);}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value==0>::type
fill_v(U &u,const V... v){
	for(auto &e:u) fill_v<T>(e,v...);
}

int main(void) {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int64 N;
  cin >> N;
  string T;
  string S = "110";
  cin >> T;

  int64 res = 0;
  REP(s, 3) {
    bool ok = 1;
    REP(i, N) {
      if (S[(s + i)%3] != T[i]) {
        ok = 0;
        break;
      }
    }
    if (ok) {
      int64 x = (N + s) % 3;
      int64 y = (30000000000LL - (3-x)%3 - N + 1);
      res += (y + 2) / 3;
    }
  }
  cout << res << endl;
}

