#include <bits/stdc++.h>
using namespace std;
long int divs(int n) {
  long int c = 0;
  for (int i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i)
        c++;
      else
        c += 2;
    }
  }
  return c;
}
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  long long int sum = 0;
  long int arr[1000002];
  memset(arr, -1, sizeof(arr));
  for (int i = 1; i <= 100; i++) {
    for (int j = 1; j <= 100; j++) {
      for (int k = 1; k <= 100; k++) {
        if (arr[i * j * k] == -1) arr[i * j * k] = divs(i * j * k);
      }
    }
  }
  for (int i = 1; i <= a; i++) {
    for (int j = 1; j <= b; j++) {
      for (int k = 1; k <= c; k++) {
        sum += arr[i * j * k];
      }
    }
  }
  cout << sum % (1073741824) << endl;
  return 0;
}
