visible points 3D

#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <sstream>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>

using namespace std;

#define MAXN 1000000

int mu[MAXN + 1],factor[MAXN + 1];

long long visible(int X, int Y){
    if(X == 0 || Y == 0) return 1;

    long long ret = 2;

    for(int i = 1;i <= min(X,Y);++i)
        ret += mu[i] * (X / i) * (Y / i);

    return ret;
}

long long visible(int X, int Y, int Z){
    long long ret = 0;

    for(int i = 1;i <= X;++i)
        ret += mu[i] * (X / i) * (Y / i) * (Z / i);

    return ret;
}

int main(){
    ios::sync_with_stdio(0);

    memset(factor,-1,sizeof factor);
    mu[1] = 1;

    for(int i = 2;i <= MAXN;++i){
        if(factor[i] == -1){
            mu[i] = -1;

            if(i <= MAXN / i)
                for(int j = i*i;j <= MAXN;j += i)
                    factor[j] = i;
        }else{
            int cont = 0,aux = i,p = factor[i];

            while(aux % p == 0 && cont < 2){
                aux /= p;
                ++cont;
            }

            if(cont == 2) mu[i] = 0;
            else mu[i] = -mu[i / p];
        }
    }

    int X,Y,Z;

    cin >> X >> Y >> Z;

    long long ans = visible(X,Y,Z) + visible(X,Y) + visible(Y,Z) + visible(Z,X);

    if(X >= 1) --ans;
    if(Y >= 1) --ans;
    if(Z >= 1) --ans;

    cout << ans << endl;

    return 0;
}