#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define pb push_back
#define F first
#define S second
#define ll long long
#define int ll
#define pii pair<int, int>
#define io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define M_PI 3.14159265358979323846
#define all(v) v.begin(), v.end()
#define pss pair<string, string>
#define no cout<<"No"<<endl;
#define yes cout<<"Yes"<<endl;
#define imp cout<<-1<<endl;
#define flu cout.flush();
#define Endl endl
const int N = 300009;
const int mod = 1e9+7;
void solve(){
int n, k;
cin>>n>>k;
vector<int>a;
for(int i=0; i<n; i++){
int x;
cin>>x;
a.pb(x);
}
for(int i=0; i<n-1; i++){
int x, y;
cin>>x>>y;
}
int ans1=0, sum1=0, ans2=0, sum2=0;
for(int i=0; i<n; i++){
if(sum1+a[i]>k){
ans1++;
sum1=a[i];
}
else{
sum1+=a[i];
}
}
reverse(all(a));
for(int i=0; i<n; i++){
if(sum2+a[i]>k){
ans2++;
sum2=a[i];
}
else{
sum2+=a[i];
}
}
cout<<min(ans1, ans2)<<endl;
//cout<<ans1<<" "<<ans2<<endl;
}
signed main(){
io;
int t=1;
//cin>>t;
while(t--){
solve();
}
}
