The police department of your city has just started its journey. Initially, they don’t have any manpower. So, they started hiring new recruits in groups.

Meanwhile, crimes keeps occurring within the city. One member of the police force can investigate only one crime during his/her lifetime.

If there is no police officer free (isn't busy with crime) during the occurrence of a crime, it will go untreated.

Given the chronological order of crime occurrences and recruit hirings, find the number of crimes which will go untreated.

Input

The first line of input will contain an integer n (1 ≤ n ≤ 105), the number of events. The next line will contain n space-separated integers.

If the integer is -1 then it means a crime has occurred. Otherwise, the integer will be positive, the number of officers recruited together at that time. No more than 10 officers will be recruited at a time.

Output

Print a single integer, the number of crimes which will go untreated.

Examples

Input

3
-1 -1 1


Output

2


Input

8
1 -1 1 -1 -1 1 1 1


Output

1


Input

11
-1 -1 2 -1 -1 -1 -1 -1 -1 -1 -1


Output

8

Note

Lets consider the second example:

  1. Firstly one person is hired. 
  2. Then crime appears, the last hired person will investigate this crime. 
  3. One more person is hired. 
  4. One more crime appears, the last hired person will investigate this crime. 
  5. Crime appears. There is no free policeman at the time, so this crime will go untreated. 
  6. One more person is hired. 
  7. One more person is hired. 
  8. One more person is hired. 



The answer is one, as one crime (on step 5) will go untreated.
T_ON = 0
DEBUG_ON = 0
MOD = 998244353


def solve():
    n = read_int()
    polices = 0
    count = 0
    for e in read_ints():
        if e > 0:
            polices += e
        else:
            if polices > 0:
                polices -= 1
            else:
                count += 1
    print(count)


def main():
    T = read_int() if T_ON else 1
    for i in range(T):
        solve()


def dbg(*xargs):
    if DEBUG_ON:
        print(*xargs)


from collections import *


#---------------------------------FAST_IO---------------------------------------

import os
import sys
from io import BytesIO, IOBase
# region fastio

BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")

#----------------------------------IO_WRAP--------------------------------------

def read_int():
    return int(input())


def read_ints():
    return list(map(int, input().split()))


def print_nums(nums):
    print(" ".join(map(str, nums)))


def YES():
    print("YES")


def Yes():
    print("Yes")


def NO():
    print("NO")


def No():
    print("No")

#----------------------------------FIB--------------------------------------

def fib(n):
    a, b = 0, 1
    for _ in range(n):
        a, b = b, a + b
    return a


def fib_ns(n):
    assert n >= 1
    f = [0 for _ in range(n + 1)]
    f[0] = 0
    f[1] = 1
    for i in range(2, n + 1):
        f[i] = f[i - 1] + f[i - 2]
    return f

#----------------------------------MOD--------------------------------------

def gcd(a, b):
    if a == 0:
        return b
    return gcd(b, a % b)


def xgcd(a, b):
    """return (g, x, y) such that a*x + b*y = g = gcd(a, b)"""
    x0, x1, y0, y1 = 0, 1, 1, 0
    while a != 0:
        (q, a), b = divmod(b, a), a
        y0, y1 = y1, y0 - q * y1
        x0, x1 = x1, x0 - q * x1
    return b, x0, y0


def modinv(a, m):
    """return x such that (a * x) % m == 1"""
    g, x, _ = xgcd(a, m)
    if g != 1:
        raise Exception('gcd(a, m) != 1')
    return x % m


def mod_add(x, y):
    x += y
    while x >= MOD:
        x -= MOD
    while x < 0:
        x += MOD
    return x


def mod_mul(x, y):
    return (x * y) % MOD


def mod_pow(x, y):
    if y == 0:
        return 1
    if y % 2:
        return mod_mul(x, mod_pow(x, y - 1))
    p = mod_pow(x, y // 2)
    return mod_mul(p, p)


def mod_inv(y):
    return mod_pow(y, MOD - 2)


def mod_div(x, y):
    # y^(-1): Fermat little theorem, MOD is a prime
    return mod_mul(x, mod_inv(y))

#---------------------------------PRIME---------------------------------------

def is_prime(n):
    if n == 1:
        return False
    for i in range(2, int(n ** 0.5) + 1):
        if n % i:
            return False
    return True


def primes(n):
    """
    generate primes of [1..n] using sieve's method
    """
    P = [True for _ in range(n + 1)]
    P[0] = P[1] = False
    for i in range(int(n ** 0.5) + 1):
        if P[i]:
            for j in range(2 * i, n + 1, i):
                P[j] = False
    return P

#---------------------------------MAIN---------------------------------------

main()
