#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <list>
#include <iterator>
#include <cmath>
#include <cstring>
using namespace std;const int maxn = 1e5+10;
int a[maxn];
const int INF = 0x3fffffff;
int n, d;int find_index(int s, int id, int & min_value) {int min_d = INF;int ret = -1;for(int i = id+1; i <= n; i++) {s += a[i];if(d-s < min_d) {min_d = d-s;ret = i;}}min_value = min_d;return ret;
}int main() {//freopen("in.txt", "r", stdin);    scanf("%d%d", &n, &d);for(int i = 1; i <= n; i++) {scanf("%d", &a[i]);}int s = 0;for(int i = 1; i <= n; i++) {s += a[i];if(s > d) {printf("-1\n");return 0;}}s = 0;int cnt = 0;int res = 0;while(cnt < n) {int pre_cnt = cnt+1;int min_value;cnt = find_index(s, cnt, min_value);int flag = 1;for(int i = pre_cnt; i <= cnt; i++) {s += a[i];if(a[i] == 0 && s < 0 && flag == 1) {s += min_value; flag = 0;res ++;}if(a[i] == 0 && s < 0 && flag == 0 ) {printf("-1\n");return 0;}}}printf("%d\n", res);            return 0;
}

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <list>
#include <iterator>
#include <cmath>
#include <cstring>
using namespace std;const int maxn = 1e5+10;
int a[maxn];
const int INF = 0x3fffffff;
int n, d;int main() {scanf("%d%d", &n, &d);for(int i = 0; i < n; i++) {scanf("%d", &a[i]);}int flag = 1;int top, bottom;int res = 0;top = bottom = 0;for(int i = 0; i < n; i++) {if(a[i] == 0) {if(top < 0) {res++;top = d;            }bottom = max(0, bottom);}else {top += a[i];bottom += a[i];top = min(top, d);if(bottom > d) {flag = -1;break;}}}if(flag == 1) {printf("%d\n", res);}else {printf("-1\n");}return 0;
}