#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main()
{
  int N;
  cin >> N;
  string s;
  cin >> s;
  if(N>=2) {
    // 00 or 11
    FOR(i,0,N-1) {
      if((s[i]=='0'&&s[i+1]=='0')||(s[i]=='1'&&s[i+1]=='1')) {
        puts("YES");
        return 0;
      }
    }
  }
  if(N>=4) {
    // 1010 or 0101
    FOR(i,0,N-3) {
      if(s[i]=='0'&&s[i+1]=='1'&&s[i+2]=='0'&&s[i+3]=='1') {
        puts("YES");
        return 0;
      }
      if(s[i]=='1'&&s[i+1]=='0'&&s[i+2]=='1'&&s[i+3]=='0') {
        puts("YES");
        return 0;
      }
    }
  }
  puts("NO");
  return 0;
}