#include <bits/stdc++.h>
using namespace std;
int d[1000003];
int main() {
  for (int i = 1; i <= 1000000; i++)
    for (int j = i; j <= 1000000; j += i) d[j]++;
  int a, b, c;
  cin >> a >> b >> c;
  int ans = 0;
  for (int i = 1; i <= a; i++)
    for (int j = 1; j <= b; j++)
      for (int k = 1; k <= c; k++) ans += (d[i * j * k]) % 1073741824;
  cout << ans % 1073741824;
  return 0;
}
