BARA BIJOY

typedef unsigned long long ll;
ll nCr(ll n , ll i)
{
    if(n<i)return 0;
    if(n==i)return 1;

    ll ans=1;
    for(ll k=n,p=1;k>(n-i);k--)
    {
        ans *= k;
        if(p<=i)
        {
            ans/=p;
            p++;
        }
    }
    return ans;
}
int main()
{

    ll i,j,n,m,t,aa=0,bb=0;
    cin>>n>>m>>t;

    for(i=t-1;i>=4;i--)
    {
        aa = nCr(n,i);
        aa *= nCr(m,t-i);

        bb+=aa;
    }

    cout<<bb<<endl;
    return 0;
}