//
//  Sieve of Eratosthenes(エラトステネスの篩)
//
/*

    計算量 O(NloglogN)

*/

#include <bits/stdc++.h>
using namespace std;
#define overload3(a,b,c,d,...) d
#define rep1(i,n) for (int i=0; i<(n); i++)
#define rep2(i,a,n) for (int i=(a); i<(n); i++)
#define rep(...) overload3(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#define rrep1(i,n) for (int i=(n-1); i>=0; i--)
#define rrep2(i,a,n) for (int i=(n-1); i>=(a); i--)
#define rrep(...) overload3(__VA_ARGS__, rrep2, rrep1)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) int((x).size())
#define pcnt __builtin_popcountll
using ll = long long;
using P = pair<ll,ll>;
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
using vi = vc<ll>;
using vvi = vv<ll>;
const int INF = 1e9;
const ll LINF = 8e18;
template<typename T>istream& operator>>(istream&i,vc<T>&v){rep(j,sz(v))i>>v[j];return i;}
template<typename T>string join(const T&v,const string& d=""){stringstream s;rep(i,sz(v))(i?s<<d:s)<<v[i];return s.str();}
template<typename T>ostream& operator<<(ostream&o,const vc<T>&v){if(sz(v))o<<join(v," ");return o;}
template<typename T1,typename T2>istream& operator>>(istream&i,pair<T1,T2>&v){return i>>v.first>>v.second;}
template<typename T1,typename T2>ostream& operator<<(ostream&o,const pair<T1,T2>&v){return o<<v.first<<","<<v.second;}
template<class T> inline bool chmax(T& a, T b) {if(a<b) { a=b;return true; } return false;}
template<class T> inline bool chmin(T& a, T b) {if(a>b) { a=b;return true; } return false;}

template <class T> string to_string(T s);
template <class S, class T> string to_string(pair<S, T> p);
string to_string(char c) { return string(1, c); }
string to_string(string s) { return s; }
string to_string(const char s[]) { return string(s); }

template <class T>
string to_string(T v) {
    if (v.empty()) return "{}";
    string ret = "{";
    for (auto x : v) ret += to_string(x) + ",";
    ret.back() = '}';
    return ret;
}
template <class S, class T>
string to_string(pair<S, T> p) {
    return "{" + to_string(p.first) + ":" + to_string(p.second) + "}";
}

void debug_out() { cout << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cout << to_string(H) << " ";
    debug_out(T...);
}

#ifdef _DEBUG
#define debug(...) debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

struct Sieve{
    int n;
    vector<int> f,primes;
    Sieve(int n=1):n(n+1),f(n+1){
        f[0] = f[1] = -1;
        for(ll i=2; i<=n; ++i){
            if(f[i]) continue;
            primes.push_back(i);
            f[i]=i;
            for(ll j=i*i; j<=n; j+=i){
                if(!f[j]) f[j]=i;
            }
        }
    }

    bool isPrime(int x){ return f[x]==x;}

    vector<int> factorList(int x){
        vector<int> res;
        while(x!=1){
            res.push_back(f[x]);
            x/=f[x];
        }
        return res;
    }

    vector<P> factor(int x){
        vector<int> fl = factorList(x);
        if(fl.size()==0) return {};
        vector<P> res(1,P(fl[0], 0));
        for(int p : fl){
            if(res.back().first == p){
                res.back().second++;
            }else{
                res.emplace_back(p,1);
            }
        }
        return res;
    }

    // mの約数を列挙、返り値は約数の個数
    int divisor(ll m, vi& a){
        ll cnt = 1; a[0] = 1;
        while(m!=1){
            ll num=1, i=f[m], temp=i;
            while(m%i==0){m/=i;num++;}
            rep(k,1,num){
                rep(j,0,cnt)a[k*cnt+j]=a[j]*temp;
                temp*=i;
            }
            cnt*=num;
        }
        sort(a.begin(),a.begin()+cnt);
        return cnt;
    }
};
Sieve sieve(15001000);

void YUKI2043(){
    ll a,b,s;
    cin >> a >> b >> s;
    vi div(500);
    ll ans = 0;
    rep(i,1,s+1){
        if(i>a*b) break;
        int cnt = sieve.divisor(i,div);
        rep(j,cnt){
            ll p = div[j];
            if(a-p+1<0 || b-i/p+1<0) continue;
            ans += (a-p+1) * (b-i/p+1);
        }
    }
    cout << ans << endl;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    YUKI2043();

}