import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.format;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;

alias sread = () => readln.chomp();
alias Point2 = Tuple!(long, "y", long, "x");

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}

enum MOD = (10 ^^ 9) + 7;

void main()
{
    long N, X;
    scan(N, X);
    auto A = aryread();
    long ans;
    if (X < A[0])
    {
        ans = A[0] - X;
        A[0] = X;
    }
    // writeln(A);
    foreach (i; 0 .. N - 1)
    {
        if (X < A[i] + A[i + 1])
        {
            long s = A[i + 1] + A[i] - X;
            // writeln(s);
            A[i + 1] -= s;
            ans += s;

        }
    }
    writeln(ans);
}
