#include <bits/stdc++.h>
using namespace std;
long long int d[1000001] = {1};
void sieve() {
  long long int i, j;
  for (i = 1; i < 1000001; ++i) {
    d[i] = 1;
  }
  for (i = 2; i < 1000001; ++i) {
    for (j = i; j < 1000001; j += i) {
      d[j]++;
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  sieve();
  long long int a, b, c, i, j, k, count = 0;
  cin >> a >> b >> c;
  for (i = 1; i <= a; ++i) {
    for (j = 1; j <= b; ++j) {
      for (k = 1; k <= c; ++k) {
        count += d[i * j * k] % 1073741824;
      }
    }
  }
  cout << count % 1073741824 << "\n";
  return 0;
}
