C.cpp

#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define EACH(it,a) for(__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)

#define DEBUG(x) { cout << #x << " = "; cout << (x) << endl; }
#define PR(a,n) { cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl; }
#define PR0(a,n) { cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl; }

#define sqr(x) ((x) * (x))
using namespace std;

long long c[111][111];

int main() {
    ios :: sync_with_stdio(false);
    FOR(i,0,100) {
        c[i][0] = 1;
        FOR(j,1,i) c[i][j] = c[i-1][j-1] + c[i-1][j];
    }
    int a, b, x;
    while (cin >> a >> b >> x) {
        long long res = 0;
        FOR(u,4,a) FOR(v,1,b) if (u + v == x)
            res += c[a][u] * c[b][v];
        cout << res << endl;
    }
    return 0;
}