T134321．计数

#include
using namespace std;
#define LL long long
int a[40];
int n,m;
int gcd(int x,int y) {
    if(y==0)return x;
    else return gcd(y,x%y);
}
LL ans=0;
void dfs(int num,int step,LL lcm) {
    if(lcm>n)return ;
    if(num==m+1){
        if(step%2==1)ans-=n/lcm;//奇数个时加上
        else if(step)ans+=n/lcm;//偶数个时减去
        return ;
    }
    dfs(num+1,step,lcm);
    LL tmp=lcm*a[num]/gcd(lcm,a[num]);//选择该数
    dfs(num+1,step+1,tmp);
}
int main () {
    scanf("%d%d",&n,&m);
    ans=n;
    for(int i=1;i<=m;++i ) {
        scanf("%d",a+i);
    }   
    dfs(1,0,1);
    printf("%lld\n",ans);
    return 0;
}