Codeforces 566F Clique in the Divisibility Graph

#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<iostream>
int n,a[2000005],f[2000005];
int read(){
    int t=0,f=1;char ch=getchar();
    while (ch<‘0‘||ch>‘9‘){if (ch==‘-‘) f=-1;ch=getchar();}
    while (‘0‘<=ch&&ch<=‘9‘){t=t*10+ch-‘0‘;ch=getchar();}
    return t*f;
}
int main(){
    n=read();int mx=0;
    for (int i=1;i<=n;i++){
        a[i]=read();
        mx=std::max(mx,a[i]);
    }
    std::sort(a+1,a+1+n);
    int ans=0;
    for (int i=1;i<=n;i++){
        f[a[i]]++;
        for (int j=a[i]+a[i];j<=mx;j+=a[i])
         f[j]=std::max(f[j],f[a[i]]);
        ans=std::max(ans,f[a[i]]);
    }
    printf("%d\n",ans);
}