#include <iostream>
#include <cstring>
#include <algorithm>
#include <iomanip>
using namespace std;

long long n;
long long x,a[100005];
long long cot = 0;
long long b = 0;
int main()
{
    cin >> n >> x;
    for(int i = 1; i <= n; i ++)
    cin >> a[i];

for(int i = 1; i < n; i++){
    if(a[i]+a[i+1] >= x){
        cot += a[i+1]+a[i]-x;
        b = a[i+1]+a[i]-x;

        a[i+1] -= a[i] + a[i+1] - x;
    
    // if(a[i+1] > b)
    // a[i+1] -= b; 
    
    // if(a[i+1] <= b)
    // a[i+1] = 0;
    
    }
else continue;

}

    cout << cot;
    
return 0;
}