#include <bits/stdc++.h>
using namespace std;

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define repn(i,b) rng(i,1,b+1)
#define pb push_back
using ll=long long;

template<class t>using vc=vector<t>;
using vi=vc<int>;

template<class t,class u>bool chmin(t&a,u b){
	if(a>b){
		a=b;
		return true;
	}else return false;
}

const int inf=INT_MAX/2-100;

int d,e,f;
ll ans;
void slv(){
	cin>>d>>e>>f;
	vc<int>p{1, 2, 3};
	do{
		vc<int>q{1, 2, 3};
		do{
			rep(mask, 8){
				rep(mask2, 8){
					vc<int>pp = p, qq = q;
					rep(i, 3){
						if(((mask>>i)&1)) pp[i] = -pp[i];
						if(((mask2>>i)&1)) qq[i] = -qq[i];
					}
					
					vc<int>r;
					rep(i,3) r.pb(abs(pp[i]-qq[i]));
					sort(r.begin(), r.end());
					bool bad = false;
					rep(i,3) if(r[i] != i+1) bad=true;
					if(bad) continue;
					vc<int>bg(2,20000000);
					chmin(bg[max(abs(pp[0]), abs(qq[0]))-2], d);
					chmin(bg[max(abs(pp[1]), abs(qq[1]))-2], e);
					chmin(bg[max(abs(pp[2]), abs(qq[2]))-2], f);
					int x = bg[0], y = bg[1];
					int z = (y+1)/2;
					if(x <= z){
						ans += (ll)(x)*(x-1)/2;
					}
					else {
						ans += (ll)(z)*(z-1)/2;
						ans += (ll)(y-z)*(y-z-1)/2;
						if(x < y-1){
							ans -= (ll)(y-x)*(y-x-1)/2;
						}
					}
				}
			}
		}while(next_permutation(q.begin(),q.end()));
	}while(next_permutation(p.begin(), p.end()));
	cout << ans/2 << endl;
}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	slv();
}