a,b,s=map(int,input().split())
div=[[] for i in range(s+1)]
for i in range(1,s+1):
  for j in range(i,s+1,i):
    div[j].append(i)

ans=0
for i in range(1,s+1):
  for j in div[i]:
    k=i//j
    if j<=a and k<=b:
      ans+=(a-j+1)*(b-k+1)

print(ans)