#include <iostream>
#include <cstring>
typedef long long ll;
using namespace std;
const int N = 1010;
ll dp[N][N];//dp[i][j]表示t串前j个字符在s串中前i个字符中出现的次数

int main()
{
    int n, m;
    cin>>n>>m;
    string s, t;   
    cin>>s>>t;

    for(int i = 0; i <= n; i ++ )
        dp[i][0] = 1;

    for(int i = 1; i <= n; i ++ )
        for(int j = 1; j <= m; j ++ )
        {
            //不选择第i个字符
            dp[i][j] = dp[i - 1][j];
            //想等了才可以选择
            if(s[i - 1] == t[j - 1])
                dp[i][j] += dp[i - 1][j - 1];
        }

    cout<<dp[n][m]<<endl;
}