#include <iostream>
using namespace std;
#define ll long long
int main(){
    ll n,s;
    cin>>n>>s;
    ll arr[100010] = {0};
    for(int i=0;i<n;i++)cin>>arr[i];

    ll ans = 0;
    for(int i=0;i<n-1;i++){
        while(arr[i]+arr[i+1]>s){
            if(arr[i+1]!=0){
                arr[i+1]--;
            }else{
                arr[i]--;
            }
            ans++;
        }
    }
    cout<<ans;
    return 0;
}