create dev channel

zeta/c/completed/24265.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int main() {
+    long long n;
+    scanf("%lld", &n);
+    printf("%lld\n%d\n", n * (n - 1L) / 2L, 2);
+    return 0;
+}