C. Coconut（2017 ACM-ICPC 亚洲区（乌鲁木齐赛区）网络赛）

额，只是一道签到题,emmm直接代码：

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

const int maxn = 1005;
int c[maxn];
int d[maxn];

int main(){
    int t;
    scanf("%d", &t);
    while (t--){
        int n, m;
        scanf("%d %d", &n, &m);
        for (int i = 0; i < n; i++){
            scanf("%d", &c[i]);
        }
        for (int i = 0; i < n - 1; i++){
            scanf("%d", &d[i]);
        }
        d[n-1] = 0;
        int ans = 0;
        int i;
        for (i = 0; i < n; i++){
            ans = ans + c[i] - m*d[i];
            if (ans < 0)
                break;
        }
        if (i == n)
            printf("Yes
");
        else 
            printf("No
");
    }
    //system("pause");
    return 0;
}