@@ -0,0 +1,23 @@
+#include<bits/stdc++.h>
+using namespace std;
+using ll = long long;
+ll Cnr(int n, int r) {
+ ll s = 1;
+ if (r * 2 > n) {
+ r = n - r;
+ }
+ for (int i = 0; i < r; i++) {
+ s *= (n - i);
+ for (int i = r; i >= 2; i--) {
+ s /= i;
+ return s;
+}
+int main() {
+ int n, r;
+ while (cin >> n >> r) {
+ cout << Cnr(n, r) << endl;
+ return 0;
