// Slower C++ solution:
#include <stdio.h>

#include <cmath>

#include <algorithm>

#include <bits/stdc++.h>

const int maxn = 1e5 + 10;

using namespace std;

int main()

{

    int n, x;

    long long a[maxn] = {0};

    cin >> n >> x;

    long long  count = 0;

    for (int i = 0; i < n; i++)

        scanf("%lld", &a[i]);

    for (int i = 0; i < n - 1; i++)

    {

        if (a[i] > x)

        {

            count += (a[i] - x);

            a[i] = x;

        }

        if (a[i] + a[i+1] > x)

        {

            count += (a[i+1] + a[i] - x);

            a[i+1] = a[i+1] - (a[i+1] + a[i] - x);

        }

    }

    cout << count << endl;

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 1.7463863772700445x):
// #pragma GCC optimize("Ofast")

// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")

// #pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/tree_policy.hpp>



#define FAST std::ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);

#define DECIMAL(n)  std::cout << std::fixed;std::cout << std::setprecision(n);

#define hell 1000000007

#define narak 998244353

#define PI 3.14159265358979323844

#define mp make_pair

#define eb emplace_back

#define pb push_back

#define fi first 

#define se second

#define all(v) v.begin(), v.end()

#define endl "\n"

#define sqr(a) (a)*(a)

#define __lcm(m,n) m*(n/__gcd(m,n))

#define inputarr(a,n) for(int xxx=0;xxx<n;++xxx) cin>>(a)[xxx]

#define sz(a) (int)a.size()

#define sl(a) (int)a.length()

#define display(x) for(auto &a:x) cout<<a<<" ";cout<<endl

#define debug cerr<<"bhau"<<endl

#define between(n,a,b) (a<=n&&n<=b)

#define elasped_time 1.0 * clock() / CLOCKS_PER_SEC 



#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)

template <typename Arg1>

void __f(const char* name, Arg1&& arg1){

    std::cerr << name << " : " << arg1 << endl;

}

template <typename Arg1, typename... Args>

void __f(const char* names, Arg1&& arg1, Args&&... args){

    const char* comma = strchr(names + 1, ',');std::cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);

}





template<typename T, typename U> static inline void amin(T &x, U y) { 

    if (y < x) 

        x = y; 

}



template<typename T, typename U> static inline void amax(T &x, U y) { 

    if (x < y) 

        x = y; 

}



template<typename T,typename U> std::ostream& operator<<(std::ostream& out, std::pair<T,U> a) {

    out<<a.fi<<" "<<a.se;

    return out;

}



template<typename T,typename U> std::istream& operator>>(std::istream& in, std::pair<T,U> &a) {

    in>>a.fi>>a.se;

    return in;

}



inline long long toint(const std::string &s) {std::stringstream ss; ss << s; long long x; ss >> x; return x;}

inline std::string tostring(long long number) {std::stringstream ss; ss << number; return ss.str();}

inline std::string tobin(long long x) {return std::bitset<63>(x).to_string();}



std::mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());



#define ll long long

#define pii std::pair<int, int>

#define vi vector<int>  

#define vvi vector<vi > 

#define vii vector<pii >

#define point complex<ll>

#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 



/*----------------------Graph Moves----------------*/

//const int fx[]={+1,-1,+0,+0};

//const int fy[]={+0,+0,+1,-1};

//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move

//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move

//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move

//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move

/*------------------------------------------------*/



//primes for hashing 937,991,1013,1409,1741



using namespace std;

using namespace __gnu_pbds;



void meowmeow321()

{

    int n,x;

    cin>>n>>x;

    int a[n];

    inputarr(a,n);

    ll ans=0;

    if(a[0]>x){

    	ans+=a[0]-x;

    	a[0]=x;

    }

    for (int i = 1; i < n; ++i) {

    	if(a[i]+a[i-1]>x){

    		ans+=a[i]+a[i-1]-x;

    		a[i]=x-a[i-1];

    	}

    }

    cout<<ans<<endl;

}

signed main()

{

    FAST;

    int testcases=1;

    //cin>>testcases;

    for(int i=0;i<testcases;++i)

    {

        meowmeow321();

    }

    cerr<<endl<<"Time Elasped : "<<elasped_time<<endl;

    return 0;

}