#include <stdio.h>
#include <string.h>
int main(){
  int N;
  char S[1000000];
  
  scanf("%d",&N);
  scanf("%s",S);
  
  if(N<=2){
    if(strcmp(S,"00")*strcmp(S,"11")==0) printf("YES\n");
    else printf("NO\n");
  }
  else if(strcmp(S,"101")*strcmp(S,"010")==0){
    printf("NO\n");
  }
  else{
    printf("YES\n");
  }
  return 0;
}