#include "testlib.h"

#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>

using namespace std;
typedef long long int ll;
ll result;
ll a[100005];
ll n, x;
char buf[256];
FILE* in, *out;
int main(int argc, char* argv[])
{
        registerGen(argc, argv, 1);

        int i = 11;

        sprintf(buf, "%d.in", i);
        in = fopen(buf, "w");
        int  box = 100000;//rnd.next(2, 100000);// 2<=n<10^5

        fprintf(in, "%d %d\n", box,0);//rnd.next(0, 1000000000) );//10^9

        for(int k = 0; k < box; k++) {
            if (k != box-1)
                fprintf(in, "%d ", rnd.next(0,1000000000));//10^9
            if (k == box-1)
                fprintf(in, "%d\n", rnd.next(0,1000000000));//10^9
        }
        fclose(in);
        in = fopen(buf, "r");//read for processing

        sprintf(buf, "%d.out", i);
        out = fopen(buf, "w");


        fscanf(in, "%lld %lld", &n, &x);

        for (int i = 1; i <= n; i++)
            fscanf(in, "%lld", a+i);

        for (int i = 1; i <= n; i++) {
            if (a[i] + a[i-1] > x) {
                result += a[i] + a[i-1] - x;
                a[i] -= (a[i] + a[i-1] -x);
            }
        }
        fprintf(out, "%lld\n", result);

        fclose(out);
        fclose(in);
        //fclose(out);


    return 0;
}