#include <bits/stdc++.h>

using namespace std;

int main()
{
   int n,m;
   cin >> n >> m;
   string S,T;
   cin >> S >> T;
   int MAX = max(n,m);
   int INF = 1000000000;
   vector<vector<int>>dp(MAX+1,vector<int>(m+1,INF));
   dp[0][0] = 0;
   for(int i = 0; i < MAX + 1; i++) dp[i][0] = i;
   for(int i = 0; i < m+1; i++) dp[0][i] = i;
   for(int i = 1; i <= n; i++)
   {
       for(int j = 1; j <= m; j++)
       {
           if(S[i-1] == T[j-1]) dp[i][j] = min(dp[i-1][j-1],dp[i][j]);
           else dp[i][j] = min(dp[i][j],min(dp[i-1][j-1]+1,min(dp[i-1][j] + 1,dp[i][j-1] + 1)));
       }
   }
   cout << dp[n][m];
}