#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;


int main() {
  int n, m;
  scanf("%d %d", &n, &m);
  char s[n+1], t[m+1];
  scanf("%s", s);
  scanf("%s", t);
  int d[n+1][m+1];
  memset(d, 0, sizeof(d));
  for (int i = 0; i < n; i++) {
    d[i][0] = i;
  }
  for (int i = 0; i < m; i++) {
    d[0][i] = i;
  }

  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      int c = s[i-1] != t[j-1];
      d[i][j] = min(d[i-1][j]+1,
                    min(d[i][j-1]+1,
                        d[i-1][j-1]+c));
    }
  }

  printf("%d\n", d[n][m]);
}