C

#include <stdio.h>

#define MAXSIZE 1010
#define max(a,b) ((a)>(b)?(a):(b))
int n, m, dp[MAXSIZE][MAXSIZE];
char a[MAXSIZE], b[MAXSIZE];

void init() {
    scanf("%d%d", &n, &m);
    scanf("%s%s", a+1, b+1);
}

int main() {
    init();

    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= m; ++j) {
            dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
            if (a[i] == b[j]) {
                dp[i][j] = max(dp[i][j], dp[i-1][j-1]+1);
            }
        }
    }
    printf("%d\n", dp[n][m]);

    return 0;
}