#include<bits/stdc++.h>
#define FILE "read"
#define MAXN 5050
#define cadd(a,b) a=add(a,b)
#define csub(a,b) a=sub(a,b)
#define cmul(a,b) a=mul(a,b)
using namespace std;
const int mod=1073741824;
int A,B,C,N,cnt,ans,check[MAXN],prime[MAXN],mu[MAXN],GCD[MAXN][MAXN];
inline int add(int a,int b){return (a+=b)>=mod?a-mod:a;}
inline int sub(int a,int b){return (a-=b)<0?a+mod:a;}
inline int mul(int a,int b){return 1LL*a*b%mod;}
inline int gcd(int a,int b){
	if(GCD[a][b]) return GCD[a][b];
	else return !b?a:gcd(b,a%b);
}
void Init(){
	mu[1]=1;  N=5000;
	for(int i=2;i<=N;++i){
		if(!check[i])  prime[++cnt]=i,mu[i]=-1;
		for(int j=1;j<=cnt&&prime[j]*i<=N;++j){
			check[prime[j]*i]=1;
			if(i%prime[j]==0)  {mu[prime[j]*i]=0; break;}
			else mu[prime[j]*i]=-mu[i];
		}
	}
	for(int i=1;i<=N;++i)for(int j=i;j<=N;++j)
		GCD[i][j]=GCD[j][i]=gcd(i,j);
}
int calc(int A,int d,int k){
	int ret=0;
	for(int i=1;i<=(A/d);++i)
		if(GCD[d*i][k]==1) cadd(ret,A/(d*i));
	return ret;
}
int main(){
	freopen(FILE".in","r",stdin);
	freopen(FILE".out","w",stdout);
	scanf("%d%d%d",&A,&B,&C);  Init();
	for(int k=1;k<=C;++k){
		int ret=0;
		for(int d=1;d<=min(A,B);++d)if(mu[d])
			cadd(ret,mul(mu[d],mul(calc(A,d,k),calc(B,d,k))));
		cmul(ret,C/k);  cadd(ans,ret);
	}
	printf("%d\n",ans);
	printf("%d\n",clock());
	return 0;
}