#include <bits/stdc++.h>
using namespace std;
const int N = 1e7;
const int mod = 2 << 30;
int df[N];
int main() {
  int i, j, k;
  int a, b, c;
  int ans = 0;
  for (i = 1; i <= 1000100; i++) {
    df[i]++;
    j = i + i;
    while (j <= 1000100) {
      df[j]++;
      j += i;
    }
    df[i] %= mod;
  }
  cin >> a >> b >> c;
  for (i = 1; i <= a; i++)
    for (j = 1; j <= b; j++)
      for (k = 1; k <= c; k++) {
        ans += df[i * j * k];
        ans %= mod;
      }
  cout << ans << endl;
  return 0;
}
