B = int(input()) N = int(input()) C = [int(input()) for _ in range(N)] low = 0 high = (sum(C)+B)//N while high-low>1e-5: l = (2*low+high)/3 r = (low+2*high)/3 ml = 0 mr = 0 for i in range(N): ml += abs(C[i]-l) mr += abs(C[i]-r) if mr>=ml: high = r else: low = l ml = 0 mr = 0 high = int(high) if high>=1: low = high-1 else: low = 0 for i in range(N): ml += abs(C[i]-low) mr += abs(C[i]-high) print(min(ml,mr))