Tickets Left After Demand

In this problem, you are given the initial number of tickets (T) and the number of hours (N). For each hour, there is a ticket demand denoted by (D_i). The tickets decrease as follows:

[ T_i = T_{i-1} - D_i \quad \text{for } 1 \leq i \leq N, ]

If at any point (T_i \leq 0), the tickets are considered to have run out, and the answer is 0. Otherwise, after processing all hours, the remaining tickets, (T_N), are output. Your task is to simulate this process and output the number of tickets left (or 0 if they run out).

inputFormat

The input is provided via standard input (stdin).

The first line contains two space-separated integers: (T) (the initial number of tickets) and (N) (the number of hours).

If (N > 0), the second line contains (N) space-separated integers representing the demands (D_1, D_2, \ldots, D_N).

outputFormat

Output a single integer via standard output (stdout) representing the number of tickets remaining after processing the demands, or 0 if the tickets run out.## sample

100 5
10 20 30 10 15

15