#include<bits/stdc++.h>

using namespace std;

int main(){
    long long a, b, max_s;
    cin >> a >> b >> max_s;
    long long ans = 0;
    for(int s=1; s<=max_s; s++){
        for(int i=1; i*i<=s; i++){
            if(s%i == 0){
                int x = i, y = s/i;
                long long val = (a-y+1)*1LL*(b-x+1);
                
                if(val > 0){
                    ans += val;
                    //cout << val << ' ' << x << ' ' << y << endl;
                }
                if(i*i != s){
                    val = (a-x+1)*1LL*(b-y+1);
                    if(val > 0){
                        ans += val;
                        //cout << val << ' ' << y << ' ' << x << endl;
                    }
                }
            }
        }
    }
    cout << ans << endl;
}