#include <bits/stdc++.h>
using namespace std;
long long int divs[1000001];
int main() {
  long long int a, b, c, i, j, k, no, sum = 0, d;
  scanf("%lld%lld%lld", &a, &b, &c);
  for (i = 1; i <= 1000000; i++) {
    for (j = i; j <= 1000000; j += i) {
      divs[j]++;
    }
  }
  for (i = 1; i <= a; i++) {
    for (j = 1; j <= b; j++) {
      for (k = 1; k <= c; k++) {
        no = i * j * k;
        d = divs[no];
        sum = (sum + d) % 1073741824;
      }
    }
  }
  printf("%lld", sum);
}
