“玲珑杯”线上赛 Round #17 河南专场 B.震惊，99%+的中国人都会算错的问题

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<cmath>
#include<set>
#include<stack>
#define ll long long
#define pb push_back
#define max(x,y) ((x)>(y)?(x):(y))
#define min(x,y) ((x)>(y)?(y):(x))
#define cls(name,x) memset(name,x,sizeof(name))
using namespace std;
const int inf=1e9+10;
const ll llinf=1e16+10;
const int maxn=1e5+10;
const int maxm=1e2+10;
const int mod=1e9+7;
ll n;
int m;
ll num[maxm];
ll gcd(ll a,ll b)
{
    if(b==0) return a;
    else return gcd(b,a%b);
}
ll ans;
void dfs(ll k,int pos,int c)
{
    if(pos==m+1)
    {
        if(c%2==1) ans+=n/k*(1<<(c-1));
        else ans-=n/k*(1<<(c-1));
        return ;
    }
    if(k<=n)
    {
        dfs(k,pos+1,c);
        k=k*num[pos]/gcd(k,num[pos]);
        dfs(k,pos+1,c+1);
    }
}
int main()
{
    //freopen("in.txt","r",stdin);
    int ncas;
    scanf("%d",&ncas);
    while(ncas--)
    {
        ans=0;
        scanf("%lld %d",&n,&m);
        for(int i=1;i<=m;i++)
            scanf("%lld",&num[i]);
        for(int i=1;i<=m;i++)
            dfs(num[i],i+1,1);
        printf("%lld\n",ans);
    }
    return 0;
}