#include <iostream>
using namespace std;
int main()
{ unsigned __int64 n,a,b,i,t=1,r=1,u=1,h=1,p=1,x,y;
cin>>n>>a>>b;
if((a==0)&&(b==0)) { cout<<1; return 0; }

if(a>b) { x=a; y=b; }
else { x=b; y=a; }

if(y==0) { for(i=n+1; i<=n+x; i++) r*=i;
for(i=2; i<=x; i++) t*=i; r/=t;
cout<<r; return 0; }

for(i=2; i<=y; i++) p*=i;
for(i=y+1; i<=x; i++) h*=i; h*=p;
for(i=n+1; i<=n+y; i++) t*=i;
for(i=n+y+1; i<=n+x; i++) u*=i; u*=t;
r=u*t/(h*p);
cout<<r;
return 0; }