#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<queue>
#include<cmath>
#include<algorithm>
using namespace std;

typedef long long ll;
const int mod=1e9+7;

int main(){
    int n,x,a;
    while(~scanf("%d%d%d",&n,&x,&a)){
        ll ans=0;
        if(a>x)
            ans+=a-x,a=x;
        while(--n){
            int b;
            scanf("%d",&b);
            if(a+b>x)
                ans+=a+b-x,a=x-a;
            else
                a=b;
        }
        printf("%lld\n",ans);
    }
    return 0;
}

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vint;
typedef vector<double> vd;
typedef vector<ll> vll;
typedef vector<string> vstr;
typedef vector<vector<int>> vvint;
typedef vector<pair<int, int>> vpii;
typedef vector<pair<ll, ll>> vpll;
typedef priority_queue<int, vector<int>, greater<int>> spqint; //小さい順に取り出し
typedef priority_queue<ll, vector<ll>, greater<ll>> spqll;     //小さい順に取り出し
typedef priority_queue<int, vector<int>, less<int>> bpqint;    //大きい順に取り出し
typedef priority_queue<ll, vector<ll>, less<ll>> bpqll;        //大きい順に取り出し

#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, a, b) for (int i = (int)a; i < (int)b; i++)
#define IREP(i, v) for (auto i = (v).begin(); i != (v).end(); i++)
#define FI first
#define SE second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define PF push_front
#define TS to_string
#define BS binary_search
#define LB lower_bound
#define UB upper_bound
#define NP next_permutation
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) (ll) x.size()
#define SP(x) setprecision((ll)x)

int INF = 1e9;
int NIL = -1;
ll MOD = 1000000007;
ll LINF = 1e18;
double EPS = 1e-9;
double PI = M_PI;
int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; } //最大公約数
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }     //最小公倍数

void yes(){ cout << "Yes" << endl;}
void no(){ cout << "No" << endl;}
//-----------------------------------------

//-----------------------------------------
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    std::chrono::system_clock::time_point start,end;
    start = std::chrono::system_clock::now();
    int n ;
    ll x ;
    cin >> n >>  x ;
    vll a(n+1,0) ;
    REP(i,n){
        cin >> a[i+1] ;
    }
    ll ans = 0 ;
    FOR(i,1,n+1){
        ll tmp = max((a[i]+a[i-1]-x),(ll)0) ;
        ans += tmp ;
        a[i] -= tmp ;
    }
    cout << ans <<endl;



    end = std::chrono::system_clock::now();
    auto elapsed = std::chrono::duration_cast< std::chrono::milliseconds >(end - start).count();
    //std::cout << elapsed <<"ms"<< std::endl;

    

    return 0;
}

