#include <cstdio>
#include <list>

using namespace std;

int main() {
	int res = 0;
	int n = 0, m = 0;
	scanf("%d %d", &n, &m);
	
	list<int> arr;
	list<int> brr;
	
	for (int i = 0, j; i < n; ++i) {
		scanf("%d", &j);
		arr.push_back(j);
	}
	
	for (int i = 0, j; i < m; ++i) {
		scanf("%d", &j);
		brr.push_back(j);
	}
	
	while (arr.size() && brr.size()) {
		if (*arr.rbegin() == *brr.rbegin()) {
			arr.pop_back();
			brr.pop_back();
		} else {
			++res;
			if (*arr.rbegin() > *brr.rbegin()) {
				// 合并 brr 的
				int x = *brr.rbegin();
				brr.pop_back();
				int& y = *brr.rbegin();
				y += x;
			} else {
				// 合并 arr 的
				int x = *arr.rbegin();
				arr.pop_back();
				int& y = *arr.rbegin();
				y += x;
			}
		}
	}
	
	printf("%d\n", res);
	
	return 0;
}