Non-Divisible Subset

problem id:--https://www.hackerrank.com/challenges/non-divisible-subset/problem

code:--

#include <bits/stdc++.h>

using namespace std;
#define ll   long long
#define      pii               std::pair<int,int>
#define      vi                std::vector<int>
#define      vll               std::vector<long long>
#define      mp(a,b)           make_pair(a,b)
#define      pb(a)             push_back(a)
#define sc(x)   scanf("%d",&x)
#define scll(x)   scanf("%lld",&x)
#define sc2(x,y)   scanf("%d%d",&x,&y)
#define sc3(x,y,z)   scanf("%d%d%d",&x,&y,&z)
#define     pf(x)   printf("%d ",x)
#define     pf2(x,y)   printf("%d %d ",x,y)
#define     pf3(x,y,z)   printf("%d %d %d ",x,y,z)
#define pfnl()   putchar('\n');
#define      each(it,s)        for(auto it = s.begin(); it != s.end(); ++it)
#define      rep(i, n)         for(int i = 0; i < (n); ++i)
#define rep2(i,j,n)   for(int i = j; i < (n); ++i)
#define      fill(a)           memset(a, 0, sizeof (a))
#define      sortA(v)          sort(v.begin(), v.end())
#define      sortD(v)          sort(v.begin(), v.end(), greater<auto>())
#define      X                 first
#define      Y                 second

#define debug(x) cerr<<"debug->"<<#x<<"::"<<x<<endl
#define debug2(x,y) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n"
#define debug3(x,y,z) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\n"
#define MOD 1000000007

int main(int argc, char **argv) {
//std::ios::sync_with_stdio(false);
int arr[100005];
int freq[105]={0};
int n,k;
sc2(n,k);
rep(i,n) sc(arr[i]);
rep(i,n) arr[i]=arr[i]%k , ++freq[arr[i]];
int upper_bound=ceil(k/2.0);
int ans=0;
//rep(i,n) pf(freq[i]);
ans=(!(k&1) && freq[upper_bound]);
ans+=(freq[0]!=0);
//debug(upper_bound);
rep2(i,1,upper_bound){
//debug2(freq[i],freq[k-i]);
ans+=max(freq[i],freq[k-i]);
}
printf("%d\n",ans);

return 0;
}