A,B,S = map(int,input().split())
AA = [0] * (A+1)
for i in range(1,A+1):
    AA[i] = (A - i + 1) + AA[i-1]
ans = 0
for i in range(1,min(S+1,B+1)):
    ans += (B -i + 1) * AA[min(S//i,A)]
print(ans)