代码：
------------
```cpp
#include <bits/stdc++.h>
using namespace std;
#define int long long
const int M = 20 + 5, N = 100 + 5, K = 1e5 + 5;
int n, B;
int a[M], b[N], c[N];
int dp[K];
signed main() {
scanf("%lld %lld", &n, &B);//输入
for (int i = 1; i <= B; i++) scanf("%lld", &a[i]);//输入
for (int i = 1; i <= n; i++) scanf("%lld", &c[i]);//输入
for (int i = 1; i <= n; i++) {
b[i] = c[i] - c[i - 1];
if (c[i - 1] != 0) b[i]++;
}//求出每一个牧场单独的声音
for (int i = 1; i <= 1e5; i++) {
dp[i] = 1e8;//记住，一定要赋值成一个极大值！！！
for (int j = 1; j <= B; j++) {
if (i >= a[j]) dp[i] = min(dp[i], dp[i - a[j]] + 1);//状态转移方程
}
}
int sum = 0;
for (int i = 1; i <= n; i++) {
if (dp[b[i]] == 1e8) {
cout << -1;
return 0;
}//输出-1
sum += dp[b[i]];//加入总和
}
cout << sum;//输出
return 0;
}
```