#include <stdio.h>

int main () {
  int n = 0;
  char s[4001] = "";
  
  int res = 0;
  
  long long ans = 0LL;
  long long mod_num = 998244353LL;
  
  long long dp[4000][4000] = {};
  long long pow2[4000] = {};
  int cnt[4000] = {};
  
  res = scanf("%d", &n);
  res = scanf("%s", s);
  
  if (n <= 1) {
    printf("%d\n", (int)(s[0]-'0'));
    return 0;
  }
  
  pow2[0] = 1LL;
  for (int i = 1; i < n; i++) {
    pow2[i] = (pow2[i-1]*2LL)%mod_num;
  }
  
  if (s[0] == '1') {
    dp[0][0] = 1LL;
    ans += pow2[n-2];
  }
  
  for (int i = 1; i < n; i++) {
    for (int j = i; j >= 0; j--) {
      if (s[j] == '1') {
        long long tmp = pow2[j];
        if (j > 0) {
          tmp += mod_num-dp[j-1][i-j];
        }
        dp[i][i-j] = tmp%mod_num;
        tmp *= pow2[i-j];
        tmp %= mod_num;
        if (i < n-1) {
          tmp *= pow2[n-2-i];
        }
        ans += tmp%mod_num;
      }
    }
    for (int j = 0; j < n; j++) {
      dp[i][j] += 2LL*dp[i-1][j];
      dp[i][j] %= mod_num;
    }
  }
  
  printf("%lld\n", ans%mod_num);
  return 0;
}