Problem Link

||Source Code||

#include<bits/stdc++.h>

using namespace std;

#define ll long long

#define fr(i,a,b) for(i=a;i<b;i++)

ll nCr(ll n,ll r)

{

ll res=1,i;

for(i=0;i<r;i++) { res*=(n-i); res/=(i+1); } return res; } int main() { ll n,i,r,t,ans=0; cin>>n>>r>>t;

for(i=4;i<t;i++)

{

ans+=nCr(n,i)*nCr(r,t-i);

}

cout<<ans<<endl;

}

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