#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
void upd(int &x,int y) {
    x = min(x , y);
}
ll S(int l,int r) {
    return 1LL*r*(r + 1) / 2 - 1LL*l*(l-1)/2;
}
ll solve(int a,int b,int c) {
    // printf("%d %d %d : ",a,b,c);
    a = min(a , b - 1);
    a = min(a , (c + 1) / 2 - 1) ;
    ll ans = 0;
    if(c - b >= 1) {
        int r = min(a , c - b);
        ans += 1LL * r * b;
        ans -= 1LL * S(1 , r) ;
    }
    int lp = max(1 , c  -b + 1) ;
    if(lp <= a) {
        ans += 1LL * (a - lp + 1) * c;
        ans -= 2LL * S(lp , a) ;
    }
    // printf("%lld\n",ans) ;
    return ans;
}
void output(__int128 x) {
    if(x < 10) {
        cout << (int)(x % 10);
        return;
    }
    output(x / 10);
    cout << (int)(x % 10);
}
int main() {
    int a,  b,  c;
    cin >> a >> b >> c;
    __int128 ans = 0;
    vector<vector<int> > v;
    // v.push_back(vector<int>{0 , 1 , 1});
    // v.push_back(vector<int>{1 , 1 , 2});
    v.push_back(vector<int>{1 , 2 , 3});
    v.push_back(vector<int>{1 , 2 , 4});
    vector<int> g(4) ;
    g[1] = a;g[2] = b;g[3] = c;
    set<vector<int> > sv;
    for(auto &x : v ) {
        auto p1 = x;
        do{
            auto p2 = x;
            do{
                for(int s1 = 0;s1 < (1 << 3);s1++) {
                    for(int s2 = 0;s2 < (1<<3);s2++) {
                        bool ff=1;
                        auto p3 = p1;
                        auto p4 = p2;
                        for(int i = 0;i < 3;i++) {
                            if(((s1 >> i) & 1) && p1[i] == 0) {ff = 0;}
                            if((s1 >> i) & 1) p3[i] *= -1;
                            if(((s2 >> i) & 1) && p2[i] == 0) {ff = 0;}
                            if((s2 >> i) & 1) p4[i] *= -1;
                        }
                        if(!ff) continue ;
                        auto p5 = p3;
                        for(int i = 0;i < 3;i++) {
                            p5[i] = abs(p5[i] - p4[i]);
                        }
                        sort(p5.begin() , p5.end()) ;
                        if(p5 != x) continue;
                        if(x==(vector<int>{1 , 2 , 4})) {
                            int lm = 1e9;
                            if(p3[0]) lm = min(lm , a / abs(p3[0]));
                            if(p3[1]) lm = min(lm , b / abs(p3[1]));
                            if(p3[2]) lm = min(lm , c / abs(p3[2]));
                            if(p4[0]) lm = min(lm , a / abs(p4[0]));
                            if(p4[1]) lm = min(lm , b / abs(p4[1]));
                            if(p4[2]) lm = min(lm , c / abs(p4[2]));
                            ans += lm;
                        }
                        else {
                            vector<int> lm(4 , 1e9) ;
                            for(int i = 0;i < 3;i++) {
                                upd(lm[abs(p3[i])] , g[i + 1]) ;
                                upd(lm[abs(p4[i])] , g[i + 1]) ;
                            }
                            ans += solve(lm[1] , lm[2] , lm[3]);
                        }
                        // vector<int> cur;
                        // for(int j = 1 ; j <= lm;j++) {
                        //     assert(abs(p3[0]) * lm <= a);
                        //     assert(abs(p3[1]) * lm <= b);
                        //     assert(abs(p3[2]) * lm <= c);
                        //     assert(abs(p4[0]) * lm <= a);
                        //     assert(abs(p4[1]) * lm <= b);
                        //     assert(abs(p4[2]) * lm <= c);
                        //     for(int k = 0;k < 3;k++) cur.push_back(p3[k] * j);
                        //     for(int k = 0;k < 3;k++) cur.push_back(p4[k] * j);
                        // }
                        // printf("%d %d %d : %d %d %d : %d\n",p3[0],p3[1],p3[2] ,p4[0],p4[1],p4[2] , lm) ;
                        // if(sv.count(cur)) {
                        //     puts("WA") ; exit(0) ;
                        // }
                        // sv.insert(cur) ;

                        // ans += lm;
                    }
                }
            }while(next_permutation(p2.begin() , p2.end()));
        }while(next_permutation(p1.begin() , p1.end()));
    }
    // for(auto &cur : sv) {
    //     vector<int> p1,p2,p3;
    //     for(int i = 0;i < 3;i++) p1.push_back(cur[i]);
    //     for(int i = 0;i < 3;i++) p2.push_back(cur[i + 3]);
    //     for(int i = 0;i < 3;i++) p3.push_back(p1[i] - p2[i]) ;
    //     for(auto &x  : p1) x = abs(x);
    //     for(auto &x  : p2) x = abs(x);
    //     for(auto &x  : p3) x = abs(x);
    //     sort(p1.begin() , p1.end());
    //     sort(p2.begin() , p2.end());
    //     sort(p3.begin() , p3.end());
    //     assert(p1 == p2 && p2 == p3) ;
    // }
    ans /= 2;
    // for(int i = 3 ; i <= min({a , b , c}) ; i++) {
    //     printf("%d %d\n",i,(i-2)-(i%2==0)) ;
    //     ans += (i - 2) - (i % 2 == 0) ;
    // }
    output(ans);
    cout<<"\n";
    // cout << ans << '\n' ; return 0;
}