Longest common subsequence

#include <cstdio>
#include <vector>
using namespace std;
int main()
{
    int n, m, i, j;
    scanf("%d", &n);
    vector <int> a(n + 1);
    for(i = 1; i <= n; i++) scanf("%d", &a[i]);
    scanf("%d", &m);
    vector <int> b(m + 1);
    for(i = 1; i <= m; i++) scanf("%d", &b[i]);
    vector < vector <int> > dp(n + 1, vector <int> (m + 1));
    for(i = 1; i <= n; i++)
    {
        for(j = 1; j <= m; j++)
        {
            if(a[i] == b[j]) dp[i][j] = dp[i - 1][j - 1] + 1;
            else dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
    }
    printf("%d", dp[n][m]);
    return 0;
}