#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int long long
#define ll long long
#define ull unsigned long long
#define lb lower_bound
#define ub upper_bound
#define IOS ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
int gcd(int a, int b){
return __gcd(a, b);
}
int lcm(int a, int b){
return a / gcd(a, b) * b;
}
void solve(){
int n, k;
cin >> n >> k;
int arr[n + 1];
for (int i = 1; i <= n; i++ )cin >> arr[i];
for (int i = 1; i <= n - 1; i++ ){
int a, b;
cin >> a >> b;
}
int ans = 0, sum = 0;
for (int i = 1; i <= n; i++){
if(sum + arr[i] > k){
ans++;
sum = arr[i];
}
else sum += arr[i];
}
cout << ans << endl;
}
signed main(){
IOS;
int t = 1;
//cin >> t;
while (t--){
solve();
}
}
