#include <iostream>
#include <string>
using namespace std;

int N, M;
string S, T;
int dp[1001][1001];

int rec(int i, int j){
    if(i < 0 || j < 0) return 0;
    if(dp[i][j] != -1) return dp[i][j];
    
    int ret = 1000001;
    if(S[i] == T[j]) ret = rec(i-1, j-1);
    else {
        ret = min(ret, rec(i-1, j) + 1);
        ret = min(ret, rec(i, j-1) + 1);
        ret = min(ret, rec(i-1, j-1) + 1);
    }
    return dp[i][j] = ret;
}

int main(void){
    // Your code here!
    for(int i = 0; i <= 1000; i++) for(int j = 0; j <= 1000; j++) dp[i][j] = -1;
    
    cin >> N >> M;
    cin >> S >> T;
    cout << rec(S.size()-1, T.size() - 1) << endl;
}