import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

import static java.lang.Math.*;
import static java.lang.String.format;

public class Main {
    public static void main(String[] args) {
        solve();
    }

    final static int INF = Integer.MAX_VALUE >> 2;
    final static int MOD = 1_000_000_007;
    final static int[] dx4 = {0, 1, 0, -1};
    final static int[] dy4 = {1, 0, -1, 0};
    final static int[] dx9 = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
    final static int[] dy9 = {-1, 0, 1, -1, 0, 1, -1, 0, 1};
    final static Runnable me = () -> {
    };

    public static void solve() {
        //TODO:Solve problem like ***
        final Scanner sc = new Scanner();
        int n = sc.nextInt();
        int x = sc.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = sc.nextInt();
        }
        long ans=0;
        for (int i = 1; i < n; i++) {
            int sum = a[i - 1] + a[i];
            if(sum<=x)continue;
            int dec=sum-x;
            ans+=dec;
            a[i] = max(0, a[i] - dec);
        }
        put(ans);
    }

    static class Encoder {
        final int mod;

        public Encoder(int mod) {
            this.mod = mod;
        }

        public int encode(int x, int y) {
            assert y < mod;
            return x * mod + y;
        }

        public int decodeX(int z) {
            return z / mod;
        }

        public int decodeY(int z) {
            return z % mod;
        }
    }

    static class Accepter<T> {
        private T val;
        private final Predicate p;

        public Accepter(T defaultValue, Predicate p) {
            this.val = defaultValue;
            this.p = p;
        }

        /**
         * @return accepted newval?
         */
        public boolean replace(T newVal) {
            if (p.test(newVal)) {
                this.val = newVal;
                return true;
            }
            return false;
        }
    }

    //runWhenEAで使う
    private static Runnable func(Object... objects) {
        try {
            assert false;
            return me;
        } catch (AssertionError e) {
            return () -> {
                put(objects);
            };
        }
    }

    private static void print(Object... objects) {
        if (objects.length == 1) {
            System.out.print(objects[0]);
        } else {
            System.out.print(Arrays.toString(objects));
        }
    }

    private static void put(Object... objects) {
        print(objects);
        put();
    }

    private static void put() {
        System.out.println();
    }


    private static void runWhenEA(Runnable runnable) {
        try {
            assert false;
        } catch (AssertionError e) {
            PrintStream ps = System.out;
            PrintStream pse = System.err;
            System.setOut(pse);
            runnable.run();
            System.setOut(ps);
        }
    }

    private static void putM(String name, char[][] mat) {
        put("---------------------" + name + "-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }

    private static void putM(String name, int[][] mat) {
        put("---------------------" + name + "-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }

    private static void putM(String name, long[][] mat) {
        put("---------------------" + name + "-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }

    private static void putM(String name, boolean[][] mat) {
        put("---------------------" + name + "-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }

    private static final class Scanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }

    private static class FixedIntPair {
        public final int x, y;
        public static final FixedIntPair ZEROS = new FixedIntPair(0, 0);

        FixedIntPair(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public String toString() {
            return format(FixedIntPair.class.getSimpleName() + ":(%d,%d)", x, y);
        }
    }

    private static final class FixedLongPair {
        public final long x, y;
        public static final FixedLongPair ZEROS = new FixedLongPair(0, 0);

        FixedLongPair(long x, long y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public int hashCode() {
            return (int) x + (int) y;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null) return false;
            if (!(obj instanceof FixedLongPair)) return false;
            FixedLongPair pair = (FixedLongPair) obj;
            return this.x == pair.x && this.y == pair.y;
        }

        @Override
        public String toString() {
            return format(FixedLongPair.class.getSimpleName() + ":(%d,%d)", x, y);
        }
    }

    private static final class Binary {
        public static String toZeroPadding(int i) {
            return format("%" + Integer.toBinaryString(-1).length() + "s", Integer.toBinaryString(i)).replace(' ', '0');
        }

        public static String toZeroPadding(long i) {
            return format("%" + Long.toBinaryString(-1).length() + "s", Long.toBinaryString(i)).replace(' ', '0');
        }
    }

    public static class BinaryIndexedTree {
        final int n;
        final long[] array;

        BinaryIndexedTree(long[] array) {
            this.n = array.length;
            this.array = new long[n];
            for (int i = 0; i < array.length; i++) {
                add(i, array[i]);
            }
        }

        BinaryIndexedTree(int[] array) {
            this.n = array.length;
            this.array = new long[n];
            for (int i = 0; i < array.length; i++) {
                add(i, array[i]);
            }
        }

        public void add(int index, long val) {
            for (; index < n; index |= index + 1) {
                array[index] += val;
            }
        }

        public long sum(int index) {
            long result = 0;
            for (; index >= 0; index = (index & (index + 1)) - 1) {
                result += array[index];
            }
            return result;
        }

        /**
         * @param array arrayが1～nの順列になっていないならば定義されない
         * @return 転倒数
         */
        public static int inv(int[] array) {
            int[] a = new int[array.length];
            BinaryIndexedTree bit = new BinaryIndexedTree(a);
            bit.add(array[0] - 1, 1);
            int result = 0;
            for (int i = 1; i < array.length; i++) {
                System.out.println(bit);
                result += i - bit.sum(array[i] - 1);
                bit.add(array[i] - 1, 1);
            }
            return result;
        }

        @Override
        public String toString() {
            long[] array = new long[n];
            for (int i = 0; i < n; i++) {
                array[i] = sum(i);
            }
            String result = "";
            result += "ruiseki:" + Arrays.toString(array) + "\n";
            array[0] = sum(0);
            for (int i = 1; i < n; i++) {
                array[i] = sum(i) - sum(i - 1);
            }
            result += "source::" + Arrays.toString(array);
            return result;
        }
    }

    private static final class Util {
        static long gcd(long a, long b) {
            a = abs(a);
            b = abs(b);
            if (a < b) {
                long tmp = a;
                a = b;
                b = tmp;
            }
            while (b != 0) {
                long r = a % b;
                a = b;
                b = r;
            }
            return a;
        }

        static int gcd(int a, int b) {
            a = abs(a);
            b = abs(b);
            if (a < b) {
                int tmp = a;
                a = b;
                b = tmp;
            }
            while (b != 0) {
                int r = a % b;
                a = b;
                b = r;
            }
            return a;
        }

        static long lcm(long a, long b) {
            long gcd = gcd(a, b);
            long result = b / gcd;
            return a * result;
        }

        static boolean isValidCell(int i, int j, int h, int w) {
            return i >= 0 && i < h && j >= 0 && j < w;
        }
    }
}































































/*
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Measured memory_bytes: 28884