#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define run ios_base::sync_with_stdio(false);cin.tie(0);
#define ll long long
#define pll pair<ll, ll>
#define ull unsigned ll
#define ld double
#define endl "\n"
#define pb push_back
#define fi first
#define se second
#define pi acos(-1)
#define N 200007
#define minimum -9223372036854775807
#define maximum -minimum
#define mod 1000000007
using namespace std;
using namespace __gnu_pbds;
template <class t>
using ordered_set=tree<t, null_type,less_equal<t>, rb_tree_tag,tree_order_statistics_node_update>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll gcd(ll a, ll b)
{
if(b==0)
return a;
return gcd(b, a%b);
}
ll lcm(ll a, ll b)
{
return a/gcd(a, b)*b;
}
bool isprime(ll n)
{
if(n==1)
return 0;
for(ll i=2; i*i<=n; i++)
{
if(n%i==0)
return 0;
}
return 1;
}
ll binpow(ll a, ll b)
{
a%=mod;
ll res=1;
while(b>0)
{
if(b%2==1)
res=(res*a)%mod;
a=(a*a)%mod;
b/=2;
}
return res;
}
int main()
{
run;
ll n, m;
cin>>n>>m;
ll a[n];
for(ll i=0; i<n; i++)
{
cin>>a[i];
}
for(ll i=1; i<n; i++)
{
ll x, y;
cin>>x>>y;
}
ll i=0, cvb=1, cur=0;
while(i<n)
{
cur+=a[i];
if(cur>m)
{
cvb++;
cur=a[i];
}
i++;
}
cout<<cvb-1<<endl;
}
// By Xanlar
// NUREDDIN <3 UZR ISTEYIREM PLS QEBUL ELE SENIN YERINDE OTURDUGUM UCUN
