4158번: CD ↗

#include <bits/stdc++.h>

#define for1(s,n) for(int i = s; i < n; i++)
#define for1j(s,n) for(int j = s; j < n; j++)
#define foreach(k) for(auto i : k)
#define foreachj(k) for(auto j : k)
#define pb(a) push_back(a)
#define sz(a) a.size()

using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef vector <int> iv1;
typedef vector <vector<int> > iv2;
typedef vector <ll> llv1;
typedef unsigned int uint;
typedef vector <ull> ullv1;
typedef vector <vector <ull> > ullv2;

int N, M;
int a, b;
int ans;
int arr_a[1100000];
int arr_b[1100000];

int main() {
  ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);


  while(1) {
    cin >> N >> M;

    ans = a = b = 0;

    if(N == 0 && M == 0) break;

    for1(0, N) {
      cin >> arr_a[i];
    }

    for1(0, M) {
      cin >> arr_b[i];
    }

    while(a < N && b < M) {
      if(arr_a[a] == arr_b[b]) {
        ans++;
        a++;
        b++;
      } else if(arr_a[a] < arr_b[b]) {
        a++;
      } else {
        b++;
      }
    }

    cout << ans << "\n";
  }
}