#include <bits/stdc++.h>
using namespace std;
const unsigned int MOD = 1073741824;
int main() {
  int a, b, c, divisors[1000001] = {};
  int result = 0;
  for (int i = 1; i <= 1000000; i++) {
    for (int j = i; j <= 1000000; j += i) {
      divisors[j]++;
    }
  }
  cin >> a >> b >> c;
  for (int i = 1; i <= a; i++) {
    for (int j = 1; j <= b; j++) {
      for (int k = 1; k <= c; k++) {
        result += divisors[i * j * k];
      }
    }
  }
  cout << result % MOD << endl;
  return 0;
}
