#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  long long sum = 0;
  const long long mod = 1073741824;
  vector<long long> dp(1000001, 0);
  for (long long i = 1; i <= a; i++)
    for (long long j = 1; j <= b; j++)
      for (long long k = 1; k <= c; k++)
        if (dp[i * j * k])
          sum = (sum + dp[i * j * k]) % mod;
        else {
          long long c = 0;
          for (int w = 1; w * w <= i * j * k; w++)
            if (i * j * k % w == 0)
              if (w == i * j * k / w)
                c++;
              else
                c += 2;
          dp[i * j * k] = c;
          sum = (sum + c) % mod;
        }
  cout << sum << endl;
  return 0;
}
