#include <iostream>
using namespace std;
int a[11111], b[11111];
int main() {
int t;
cin >> t;
while (t --> 0) {
int n;
cin >> n;
for(int i = 0; i < n; ++i)
cin >> a[i];
for(int i = 0; i < n; ++i)
cin >> b[i];
int ans = 0, last = 0;
for(int i = 0; i < n; ++i) {
if (a[i] >= last + b[i])
ans++;
last += b[i];
if (last > a[i])
last = a[i];
}
cout << ans << "\n";
}
return 0;
}
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