#include <bits/stdc++.h>

using namespace std;

int n, a[100010], b[100010];
int f[10010][10010];

void dp()
{
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
			if (a[i - 1] == b[j - 1])
				f[i][j] = f[i - 1][j - 1] + 1;
			else
				if (f[i][j - 1] >= f[i - 1][j])
					f[i][j] = f[i][j - 1];
				else
					f[i][j] = f[i - 1][j];
}

int main()
{
	scanf("%d", &n);
	for (register int i = 0; i < n; i++)
		scanf("%d", &a[i]);
	for (register int i = 0; i < n; i++)
		scanf("%d", &b[i]);
	for (register int i = 0; i <= n; i++)
		f[i][0] = f[i][0] = 0;
	dp();
	cout << f[n][n] << endl;
	return 0;
}

怎么写成一维的数组呀？