x=int(input())
n=int(input())
v=[]
for i in range(n):
v.append(int(input()))
if(sum(v)%x==0):
print(0)
else:
count=1
k=1
v.sort()
i=n-1
while(i>=0):
if(v[i]%x==0):
i-=1
else:
v[i]+=k
k+=1
count+=1
i-=1
if(sum(v)%x==0):
print(count)
break
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