#include <bits/stdc++.h>
using namespace std;
long long NOD[1000000 + 20];
void sieve() {
  for (int i = 1; i <= 1000000 + 10; i++)
    for (int j = i; j <= 1000000 + 10; j += i) NOD[j]++;
}
int main() {
  sieve();
  int a, b, c;
  cin >> a >> b >> c;
  long long sum = 0;
  for (int i = 1; i <= a; i++)
    for (int j = 1; j <= b; j++)
      for (int k = 1; k <= c; k++) {
        sum += NOD[i * j * k];
        sum %= 1073741824;
      }
  cout << sum << endl;
  return 0;
}
