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

int main(){
    int64_t res = 0;
    int64_t A, B, S; cin >> A >> B >> S;
    for(int64_t C = 1; C <= min(A, S); C++){
        int64_t part1 = (A - C + 1);
        int64_t part2 = (B + 1) * min(B, S / C);
        int64_t part3 = (min(B, S / C) * (min(B, S / C)+1) / 2);
        res += part1 * (part2 - part3);
    }
    cout << res << '\n';
}