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