#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define fi first
#define in inline
#define se second
#define pb push_back
const int N = 1e5+10;

ll read(){
	ll x = 0,f = 1;char c = getchar();
	for(;c < '0' || c > '9';c = getchar())if(c == '-')f = -1;
	for(;c >= '0' && c <= '9';c = getchar())x = (x<<1) + (x<<3) + c-'0';
	return x * f;
}

int n;
int a[N],v[N<<1],ans;
int main(){
	freopen("teen.in","r",stdin);
	freopen("teen.out","w",stdout);
	n = read();
	for(int i = 0;i <= 2 * n;i++)v[i] = 1e8;
	int s = n;
	v[n] = 0;
	for(int i = 1;i <= n;i++){
		a[i] = read();
		s += (a[i] == 1 ? 1 : -1);
		if(v[s] != 1e8)ans = max(ans,i - v[s]);
		else v[s] = i;
	}
	printf("%d\n",ans);

	return 0;

}