容斥原理 第一题 水！
代码：
#include<iostream>
#include<cstring>
#include<cstdio>
#include<string>
#include<set>
#include<map>
#include<cmath>
#include<algorithm>
#include<vector>
#include<cmath>
#include<queue>
#include<stack>
//#define ull unsigned long long
#define ll long long
using namespace std;
const int INF=0x3f3f3f3f;
const int MOD=1000000007;
const double eps=1e-6;
const int N=50;
ll gcd(ll x,ll y)
{
if(x%y==0)
return y;
return gcd(y,x%y);
}
ll lcm(ll x,ll y)
{
return x*y/gcd(x,y);
}
ll a[N];
ll solve(ll *a,int n,ll M)
{
ll sum=0;
for(int k=1;k<(1<<n);++k)
{
ll LCM=1;
int num=0;
for(int i=0;i<n;++i)
{
if(k&(1<<i))
{
++num;
LCM=lcm(LCM,a[i]);
}
}
if((num&1)==1)
{
sum+=(M/LCM);
}else
{
sum-=(M/LCM);
}
}
return sum;
}
int main()
{
//freopen("data.in","r",stdin);
ll n;
int m;
while(cin>>n>>m)
{
for(int i=0;i<m;++i)
cin>>a[i];
cout<<(n-solve(a,m,n))<<endl;
}
return 0;
}