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

signed main(){
    int a, b, max_s;
    cin >> a >> b >> max_s;
    long long ans = 0;
    for(int i=1; i<=max_s; i++){
        for(int j=1; j*j<=i; j++){
            if(i%j == 0){
                int x = j, y = i / j;
                if((a-y+1) > 0 and (b-x+1) > 0){
                    ans += (a-y+1)*1LL*(b-x+1);
                }
                if(j*j == i)break;
                if((a-x+1) > 0 and (b-y+1) > 0){
                    ans += (a-x+1)*1LL*(b-y+1);
                }
            }
        }
    }
    cout << ans << '\n';
}