#include<bits/stdc++.h>
using namespace std;

//#define int long long

typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
template<class T,class U>void chmin(T &t,U f){if(t>f)t=f;}
template<class T,class U>void chmax(T &t,U f){if(t<f)t=f;}

int N;
int A[100000];

signed main(){
    cin>>N;
    rep(i,N)cin>>A[i];

    vint vec;
    rep(i,N){
        if(i>0&&A[i-1]!=A[i])continue;
        int c=i+1;
        while(c<N&&A[c-1]!=A[c])c++;
        vec.pb(c-i);
    }

    if(vec.size()<=2){
        cout<<accumulate(all(vec),0ll)<<endl;
        return 0;
    }
    int ma=0;
    rep(i,vec.size()-2){
        chmax(ma,vec[i]+vec[i+1]+vec[i+2]);
    }
    cout<<ma<<endl;
    return 0;
}