答案無非那麼幾種，要麼都用2，要麼都用3，要麼3主2補，要麼2主3補。

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<iomanip>
using namespace std;
const int maxn = 1e5 + 12;
#define ll long long int 
int main() {
    ll n, p2, p3, ans, tmp;
    scanf("%lld %lld %lld"
 
, &n, &p2, &p3);
    tmp = min(p2, p3);
    ans = min(n / 3 * p3 + (n % 3 ? tmp : 0), n / 2 * p2 + (n % 2 ? tmp : 0));
    if (n % 3 == 1) ans = min(ans, (n - 4) / 3 * p3 + 2 * p2);
    if (n % 2 == 1) ans = min(ans, (n - 3) / 2 * p2 + p3);
    printf("%lld\n", ans);


    return 0;
}