include <bits/stdc++.h>

using namespace std;
typedef long long ll;
const ll M=1e18;
int n,k;
__int128 res;
int main()
{
while(scanf("%d%d",&n,&k)!=EOF)
{
res=1;
if(k>n/2)
k=n-k;
bool f=0;
for(int i=1;i<=k;i++)
{
res=res*(n-i+1)/i;
if(res>M)
{
f=1;
break;
}
}//cout<<res<<endl;
if(f)
printf("%lld\n",M);
else
cout<<(ll)res<<endl;
}
return 0;
}