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

int N, M;
string S, T;
int dp[1005][1005];
static const int INF = 10000000;

int min(int x, int y, int z) 
{ 
    return min(min(x, y), z); 
} 

int rec(int i, int j){
    if(dp[i][j] != INF) return dp[i][j];
    if(i < 0 || j < 0) return 0;
    if(i == 0 && j == 0) return 0;
    if(i == 0 && j > 0) return j;
    if(j == 0 && i > 0) return i;

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

int main(void){
    for(int i = 0; i <= 1004; i++) for(int j = 0; j <= 1004; j++) dp[i][j] = INF;
    
    cin >> N >> M;
    cin >> S >> T;
    cout << rec(S.size(), T.size()) << endl;
}