#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <string>
#include <utility>
#include <tuple>
#include <set>
#include <map>
#include <cassert>

using namespace std;

const int mod = 998244353;

using VL = vector<long long>;
using VVL = vector<VL>;
using VVVL = vector<VVL>;

int main() {
	int n;
	string s;
	cin >> n >> s;

	if (s.find("LR") != string::npos) {
		cout << 0 << endl;
		return 0;
	}

	// [iまでみた][棒の状態 LRUの順]
	VVL dp(n+1, VL(4, 0));
	dp[0][2] = 1;  // 初期は倒れていない

	for (int i = 0; i < n; i++) {
		if (s[i] == 'L') {
			dp[i+1][0] = dp[i][0] + dp[i][2];  // 右はだめ
		} else if (s[i] == 'R') {
			dp[i+1][1] = dp[i][0] + dp[i][1] + dp[i][2];
		} else if (s[i] == 'U') {
			dp[i+1][2] = dp[i][0] + dp[i][1] + dp[i][2];
		} else {
			// dot
			dp[i+1][0] = dp[i][0] + dp[i][2];  // 右はだめ
			dp[i+1][1] = dp[i][0] + dp[i][1] + dp[i][2];
			dp[i+1][2] = dp[i][0] + dp[i][1] + dp[i][2];
		}


		for (int j = 0; j < 3; j++) {
			dp[i+1][j] %= mod;
		}
	}

	long long ans = 0;
	ans += dp.back()[0];
	ans += dp.back()[1];
	ans += dp.back()[2];
	ans %= mod;

	cout << ans << endl;
	return 0;
}