#include <stdio.h>

const int Mod = 998244353;

int main()
{
	int N;
	char S[1501];
	scanf("%d", &N);
	scanf("%s", S);
	
	int i, j, cur, prev;
	long long _dp[2][4501] = {}, *dp[2] = {&(_dp[0][3000]), &(_dp[1][3000])};
	for (i = 0, cur = 1, prev = 0, dp[0][0] = 1; i < N; i++, cur ^= 1, prev ^= 1) {
		if (S[i] == '0') {
			for (j = -i * 2; j < 0; j += 2) {
				dp[cur][j-2] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			for (j = -i * 2 + 1; j < -1; j += 2) {
				dp[cur][j+1] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			dp[cur][1] += (dp[prev][-1] + dp[prev][0]) % Mod;
			dp[prev][-1] = 0;
			dp[prev][0] = 0;
			dp[cur][-2] += dp[prev][1] % Mod;
			dp[prev][1] = 0;
			for (j = 2; j <= i; j += 2) {
				dp[cur][j+1] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			for (j = 3; j <= i; j += 2) {
				dp[cur][j-2] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
		} else if (S[i] == '1') {
			for (j = -i * 2; j < 0; j += 2) {
				dp[cur][j+1] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			for (j = -i * 2 + 1; j < 0; j += 2) {
				dp[cur][j] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			dp[cur][0] += dp[prev][0] % Mod;
			dp[prev][0] = 0;
			for (j = 1; j <= i; j += 2) {
				dp[cur][j+1] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			for (j = 2; j <= i; j += 2) {
				dp[cur][j] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
		} else {
			for (j = -i * 2; j < 0; j += 2) dp[cur][j-2] += dp[prev][j] % Mod;
			for (j = -i * 2 + 1; j < -1; j += 2) dp[cur][j+1] += dp[prev][j] % Mod;
			dp[cur][1] += (dp[prev][-1] + dp[prev][0]) % Mod;
			dp[cur][-2] += dp[prev][1] % Mod;
			for (j = 2; j <= i; j += 2) dp[cur][j+1] += dp[prev][j] % Mod;
			for (j = 3; j <= i; j += 2) dp[cur][j-2] += dp[prev][j] % Mod;
			
			for (j = -i * 2; j < 0; j += 2) {
				dp[cur][j+1] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			for (j = -i * 2 + 1; j < 0; j += 2) {
				dp[cur][j] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			dp[cur][0] += dp[prev][0] % Mod;
			dp[prev][0] = 0;
			for (j = 1; j <= i; j += 2) {
				dp[cur][j+1] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
			for (j = 2; j <= i; j += 2) {
				dp[cur][j] += dp[prev][j] % Mod;
				dp[prev][j] = 0;
			}
		}
	}
	
	long long ans = 0;
	for (i = 0; i <= N; i++) if (i % 4 == 3 || i % 4 == 0) ans += dp[prev][i];
	printf("%lld\n", ans % Mod);
	fflush(stdout);
	return 0;
}