var
i,s3,s4,s,s1,s2,n,a,b:Longint;
begin
read(n,a,b);
 s:=1;
s1:=1;
 s2:=1;
 s3:=1;
 s4:=1;
for i:=1 to n+a do
 s:=s*i;
for i:=1 to n+b do
s1:=s1*i;
for i:=1 to n do
 s2:=s2*i;
for i:=1 to a do
s3:=s3*i;
for i:=1 to b do
s4:=s4*i;
write((s*s1)/(s2*s3*s4*s2));
end.