candie.cpp

#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;

int main() {
  long long n, x, v[1000000];
  unsigned long long cnt = 0;
  cin >> n >> x;
  for (int i = 0; i < n; ++i)
    cin >> v[i];
  
  for (int i = 0; i < n-1; ++i) {
    long long rem = v[i] + v[i+1] - x;
    if (rem < 0)
      continue;
    if (rem > v[i+1]) {
      v[i] = v[i] - (v[i+1] - rem); 
      v[i+1] = 0;
      cnt += rem;
    }
    else {
      v[i+1] -= rem;
      cnt += rem;
    }
  }
  cout << cnt << endl;

}