#

# 　　  ⋀_⋀　 

#　　  (･ω･)  

# .／ Ｕ ∽ Ｕ＼

#  │＊　合　＊│

#  │＊　格　＊│ 

#  │＊　祈　＊│ 

#  │＊　願　＊│ 

#  │＊　　　＊│ 

#      ￣

#

import sys

sys.setrecursionlimit(10**6)

input=sys.stdin.readline

from math import floor,ceil,sqrt,factorial,log #log2ないｙｐ

from heapq import heappop, heappush, heappushpop

from collections import Counter,defaultdict,deque

from itertools import accumulate,permutations,combinations,product,combinations_with_replacement

from bisect import bisect_left,bisect_right

from copy import deepcopy

inf=float('inf')

mod = 10**9+7

def pprint(*A): 

    for a in A:     print(*a,sep='\n')

def INT_(n): return int(n)-1

def MI(): return map(int,input().split())

def MF(): return map(float, input().split())

def MI_(): return map(INT_,input().split())

def LI(): return list(MI())

def LI_(): return [int(x) - 1 for x in input().split()]

def LF(): return list(MF())

def LIN(n:int): return [I() for _ in range(n)]

def LLIN(n: int): return [LI() for _ in range(n)]

def LLIN_(n: int): return [LI_() for _ in range(n)]

def LLI(): return [list(map(int, l.split() )) for l in input()]

def I(): return int(input())

def F(): return float(input())

def ST(): return input().replace('\n', '')

def main():

    N,x = MI()

    A=LI()

    ans = 0

   

    for i in range(N-1):

      if A[i]+A[i+1]>x:

        s=A[i]+A[i+1]

        A[i+1]-=min(A[i+1],s-x)

        ans += max(0,s-x)



    print(ans)

if __name__ == '__main__':

    main()

#

# 　　  ⋀_⋀　 

#　　  (･ω･)  

# .／ Ｕ ∽ Ｕ＼

#  │＊　合　＊│

#  │＊　格　＊│ 

#  │＊　祈　＊│ 

#  │＊　願　＊│ 

#  │＊　　　＊│ 

#      ￣

#

import sys

sys.setrecursionlimit(10**6)

input=sys.stdin.readline

from math import floor,sqrt,factorial,hypot,log #log2ないｙｐ

from heapq import heappop, heappush, heappushpop

from collections import Counter,defaultdict,deque

from itertools import accumulate,permutations,combinations,product,combinations_with_replacement

from bisect import bisect_left,bisect_right

from copy import deepcopy

from fractions import gcd

from random import randint

def ceil(a,b): return (a+b-1)//b

inf=float('inf')

mod = 10**9+7

def pprint(*A): 

    for a in A:     print(*a,sep='\n')

def INT_(n): return int(n)-1

def MI(): return map(int,input().split())

def MF(): return map(float, input().split())

def MI_(): return map(INT_,input().split())

def LI(): return list(MI())

def LI_(): return [int(x) - 1 for x in input().split()]

def LF(): return list(MF())

def LIN(n:int): return [I() for _ in range(n)]

def LLIN(n: int): return [LI() for _ in range(n)]

def LLIN_(n: int): return [LI_() for _ in range(n)]

def LLI(): return [list(map(int, l.split() )) for l in input()]

def I(): return int(input())

def F(): return float(input())

def ST(): return input().replace('\n', '')



def main():

    N,X=MI()

    A=LI()

    ans = 0

    for i,a in enumerate(A):

        if a>X:

            ans += A[i]-X

            A[i]=X

    for i,a in enumerate(A[1:],start=1):

        if a+A[i-1]>X:

            sub = (a+A[i-1])-X

            A[i]-=min(a,sub)

            ans += min(a,sub)

            if A[i-1]+A[i]>X:

                sub = (A[i]+A[i-1])-X

                A[i-1]-=sub

                ans += sub



    print(ans)

    

if __name__ == '__main__':

    main()

#
# 　　  ⋀_⋀
# 　　  (･ω･)
# .／ Ｕ ∽ Ｕ＼
#  │＊　合　＊│
#  │＊　格　＊│
#  │＊　祈　＊│
#  │＊　願　＊│
#  │＊　　　＊│
#      ￣
#
import sys

sys.setrecursionlimit(10**6)
input = sys.stdin.readline
from math import floor, ceil, sqrt, factorial, log  # log2ないｙｐ
from heapq import heappop, heappush, heappushpop
from collections import Counter, defaultdict, deque
from itertools import (
    accumulate,
    permutations,
    combinations,
    product,
    combinations_with_replacement,
)
from bisect import bisect_left, bisect_right
from copy import deepcopy

inf = float("inf")
mod = 10**9 + 7


def pprint(*A):
    for a in A:
        print(*a, sep="\n")


def INT_(n):
    return int(n) - 1


def MI():
    return map(int, input().split())


def MF():
    return map(float, input().split())


def MI_():
    return map(INT_, input().split())


def LI():
    return list(MI())


def LI_():
    return [int(x) - 1 for x in input().split()]


def LF():
    return list(MF())


def LIN(n: int):
    return [I() for _ in range(n)]


def LLIN(n: int):
    return [LI() for _ in range(n)]


def LLIN_(n: int):
    return [LI_() for _ in range(n)]


def LLI():
    return [list(map(int, l.split())) for l in input()]


def I():
    return int(input())


def F():
    return float(input())


def ST():
    return input().replace("\n", "")


def main():
    N, x = MI()
    A = LI()
    ans = 0
    for i in range(N - 1):
        if A[i] + A[i + 1] > x:
            s = A[i] + A[i + 1]
            A[i + 1] -= min(A[i + 1], s - x)
            ans += max(0, s - x)
    print(ans)


if __name__ == "__main__":
    main()

#
# 　　  ⋀_⋀
# 　　  (･ω･)
# .／ Ｕ ∽ Ｕ＼
#  │＊　合　＊│
#  │＊　格　＊│
#  │＊　祈　＊│
#  │＊　願　＊│
#  │＊　　　＊│
#      ￣
#
import sys

sys.setrecursionlimit(10**6)
input = sys.stdin.readline
from math import floor, sqrt, factorial, hypot, log  # log2ないｙｐ
from heapq import heappop, heappush, heappushpop
from collections import Counter, defaultdict, deque
from itertools import (
    accumulate,
    permutations,
    combinations,
    product,
    combinations_with_replacement,
)
from bisect import bisect_left, bisect_right
from copy import deepcopy
from fractions import gcd
from random import randint


def ceil(a, b):
    return (a + b - 1) // b


inf = float("inf")
mod = 10**9 + 7


def pprint(*A):
    for a in A:
        print(*a, sep="\n")


def INT_(n):
    return int(n) - 1


def MI():
    return map(int, input().split())


def MF():
    return map(float, input().split())


def MI_():
    return map(INT_, input().split())


def LI():
    return list(MI())


def LI_():
    return [int(x) - 1 for x in input().split()]


def LF():
    return list(MF())


def LIN(n: int):
    return [I() for _ in range(n)]


def LLIN(n: int):
    return [LI() for _ in range(n)]


def LLIN_(n: int):
    return [LI_() for _ in range(n)]


def LLI():
    return [list(map(int, l.split())) for l in input()]


def I():
    return int(input())


def F():
    return float(input())


def ST():
    return input().replace("\n", "")


def main():
    N, X = MI()
    A = LI()
    ans = 0
    for i, a in enumerate(A):
        if a > X:
            ans += A[i] - X
            A[i] = X
    for i, a in enumerate(A[1:], start=1):
        if a + A[i - 1] > X:
            sub = (a + A[i - 1]) - X
            A[i] -= min(a, sub)
            ans += min(a, sub)
            if A[i - 1] + A[i] > X:
                sub = (A[i] + A[i - 1]) - X
                A[i - 1] -= sub
                ans += sub
    print(ans)


if __name__ == "__main__":
    main()

-from math import floor, ceil, sqrt, factorial, log  # log2ないｙｐ +from math import floor, sqrt, factorial, hypot, log  # log2ないｙｐ +from fractions import gcd +from random import randint + + +def ceil(a, b): +    return (a + b - 1) // b + -    N, x = MI() +    N, X = MI() -    for i in range(N - 1): -        if A[i] + A[i + 1] > x: -            s = A[i] + A[i + 1] -            A[i + 1] -= min(A[i + 1], s - x) -            ans += max(0, s - x) +    for i, a in enumerate(A): +        if a > X: +            ans += A[i] - X +            A[i] = X +    for i, a in enumerate(A[1:], start=1): +        if a + A[i - 1] > X: +            sub = (a + A[i - 1]) - X +            A[i] -= min(a, sub) +            ans += min(a, sub) +            if A[i - 1] + A[i] > X: +                sub = (A[i] + A[i - 1]) - X +                A[i - 1] -= sub +                ans += sub