1433E-TwoRoundDances.cpp

#include <cstdio>
typedef long long ll;

ll fact(ll x){
    ll res(1);
    for(long p = 1; p <= x; p++){res *= p;}
    return res;
}

int main(){

    ll n; scanf("%lld", &n);
    ll ans = fact(n) / (n / 2) / (n / 2) / 2;
    printf("%lld\n", ans);

    return 0;
}