const [n, k] = require("fs").readFileSync(0, "utf8").toString().trim().split(' ').map(Number);
console.log(Array.from({length:k}, (_,i) => n-i).reduce((acc,v) => acc*v,1) / Array.from({length:k}, (_,i) => i+1).reduce((acc,v) => acc*v,1));