1 #include<stdio.h>
2 #include<string.h>
3 long long int ans,n;
4 int cnt,a[25];
5 long long int gcd(long long int x,long long int y)
6 {
7 if (y==0) return x;
8 return gcd(y,x%y);
9 }
10 void dfs(int now,int flag,long long bei)
11 {
12 if (flag) ans+=n/bei;
13 else ans-=n/bei;
14 for (int i=now+1;i<=cnt;i++)
15 dfs(i,1-flag,a[i]/gcd(a[i],bei)*bei);
16 }
17 int main()
18 {
19 int m,i;
20 while (~scanf("%I64d%d",&n,&m))
21 {
22 cnt=0;
23 for (i=1;i<=m;i++)
24 {
25 scanf("%d",&a[i]);
26 if (a[i]!=0) {cnt++; a[cnt]=a[i]; }
27 }
28 ans=0; n--;
29 for (i=1;i<=cnt;i++) dfs(i,1,a[i]);
30 printf("%I64d\n",ans);
31 }
32 }
http://acm.hdu.edu.cn/showproblem.php?pid=1796
