#include <bits/stdc++.h>
using namespace std;
bool primes[1000006];
unsigned long long divis[1000006];
void sieve() {
  for (int i = 1; i <= 1000006; ++i) primes[i] = 1;
  for (int i = 2; i * i <= 1000006; i++) {
    if (primes[i])
      for (int j = 2 * i; j <= 1000006; j += i) primes[j] = 0;
  }
}
void noDivis() {
  for (int i = 1; i < 1000006; ++i)
    for (int j = i; j < 1000006; j += i) divis[j]++;
}
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  for (int i = 1; i < 1000006; ++i) divis[i] = 0;
  noDivis();
  unsigned long long s = 0;
  for (int i = 1; i <= a; ++i)
    for (int j = 1; j <= b; ++j)
      for (int k = 1; k <= c; ++k) {
        long temp = i * j * k;
        s += divis[temp];
        s %= 1073741824LL;
      }
  cout << s << endl;
  return 0;
}
