#include <iostream>
using namespace std;
char a[5000005], b[5000005]; int dp[5000005], PMAC[505];
int main() {
int n, m, seele=0, t; cin >> n >> m; for (int i=1; i<=n; i++) cin >> a[i]; for (int i=1; i<=m; i++) cin >> b[i]; dp[0] = 1;
for (int i=1; i<=m; i++) {if (b[i] == 'u') {dp[i] = dp[i-1] + (seele < n); PMAC[a[n-seele++]] += (seele < n); continue;} t = PMAC[b[i]]; dp[i] = (((PMAC[b[i]] = dp[i-1]) << 1) % 19260817 + 19260817 - t) % 19260817;}cout << dp[m];}

马蜂不要管，我觉得这样好看，习惯了。

UB 不要管，我觉得很优美。