import std.stdio;
import std.string;
import std.conv;
import std.algorithm;
import std.range;

void main(){
    int n = readln.chomp.to!int;
    int[] a = readln().split().map!(to!int).array;
    int[] x = [0,0,0];
    foreach(i; 0..n-1){
        if(a[i] == a[i+1]){
            x ~= i+1;
        }
    }
    x ~= n;
    int ans = 0;
    foreach(i; 0..x.length-3){
        ans = max(ans, x[i+3] - x[i]);
    }
    writeln(ans);
}