#include <bits/stdc++.h>
using namespace std;
long long a[10000001], i, j;
void divisor() {
  for (i = 1; i <= 1000000; i++) {
    for (j = i; j <= 1000000; j += i) a[j]++;
  }
}
int main() {
  divisor();
  long aa, b, c;
  while (cin >> aa >> b >> c) {
    long long ans = 0, i, j, k, d;
    for (i = 1; i <= aa; i++) {
      for (j = 1; j <= b; j++) {
        for (k = 1; k <= c; k++) {
          d = i * j * k;
          ans += a[d];
          ans = ans % 1073741824;
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}
