#include <bits/stdc++.h>
using namespace std;
vector<long long> v1, v2;
int main()
{
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        int a;
        cin >> a;
        v1.push_back(a);
    }
    for (int i = 1; i <= m; i++)
    {
        int b;
        cin >> b;
        v2.push_back(b);
    }
    auto it = v1.begin();
    auto at = v2.begin();
    long long count = 0;
    while (1)
    {
        if (*it != *at)
        {
            if (*it > *at)
            {
                *at += *(at + 1);
                v2.erase(at + 1);
                count++;
            }
            else
            {
                *it += *(it + 1);
                v1.erase(it + 1);
                count++;
            }
        }
        else
        {
            if (it == v1.end() - 1)
                break;
            else
            {
                it++;
                at++;
            }
        }
    }
    cout << count << '\n';
    return 0;
}

//贪心一下只需要使每个指针所在位置的值的大小一样就滑动两个指针