from collections import deque

n, m = map(int, input().split())
A = list(map(int, input().split()))

B = deque([i + 1 for i in range(n)])
for i in range(m):
    a = A[i]
    C = deque()
    for j in range(a - 1):
        idx = B.popleft()
        C.append(idx)
    f = B.popleft()
    for _ in range(a - 1):
        idx = C.pop()
        B.appendleft(idx)
    B.appendleft(f)
print(B.popleft())