#include <bits/stdc++.h>
using namespace std;
int s[1000001];
int main() {
  for (int i = 1; i <= 1000001; i++) s[i] = 1;
  for (int i = 1; i <= 1000001; i++)
    for (int j = i * 2; j <= 1000001; j += i) s[j]++;
  long long tong = 0;
  int a, b, c;
  cin >> a >> b >> c;
  for (int i = 1; i <= a; i++)
    for (int j = 1; j <= b; j++)
      for (int k = 1; k <= c; k++) tong += s[i * j * k] % 1073741824;
  cout << tong;
}
