289B - Polo the Penguin and Matrix - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;

#define int ll
#define ll long long
#define pi pair<int, int>
#define vii vector<pi>
#define vi vector<int>
#define vvi vector<vi>
#define vpi vector<pi>
#define all(x) x.begin(),x.end()
#define print(x) cout<<(#x)<<" : "<<x<<endl;
#define pb push_back
#define sti stack<int>
#define mii map<int,int>
#define uii unordered_map<int,int>
#define uci unordered_map<char,int>
#define umsi unordered_map<string,int>
#define si set<int>
#define usi unordered_set<int>
#define pqb priority_queue<int>
#define pqs priority_queue<int,vi,greater<int> >
#define len(s) s.length()
#define w(x) int x; cin>>x; while(x--)
#define mod 1000000007
#define inf 1e18
#define fp(x,y) fixed<<setprecision(y)<<x
#define sum(v,i) accumulate(all(v),i)
#define mk(arr,n,type)  type *arr=new type[n];
#define mem(a,b) memset(a, b, sizeof a)
#define iota(v,i) iota(all(v),i)
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define el "\n"
#define bug(...)       __f (#__VA_ARGS__, __VA_ARGS__)
#define vinn(name,N) int N;cin>>N;vi name(N);rep(i,0,N){cin>>name[i];}
#define vin(name,N) vi name(N);rep(i,0,N) cin>>name[i];
#define show(V) for(auto&i:V){cout<<i<<" ";}cout<<el;
#define flush cin.ignore(numeric_limits<streamsize>::max(), '\n') // clear buffer
#define rep(i,a,b) for(ll i=a;i<b;i++)
#define rep2(i,m) for(auto &i:m)
#define rep3(i,m) for(auto i:m)
#define repr(i,a,b) for(int i=a;i>b;i--)
int max(int n1, int n2) {
	return n1 > n2 ? n1 : n2;
}


template <typename Arg1>
void __f (const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << endl; }
template <typename Arg1, typename... Args>
void __f (const char* names, Arg1&& arg1, Args&&... args)
{
	const char* comma = strchr (names + 1, ',');
	cout.write (names, comma - names) << " : " << arg1 << " | "; __f (comma + 1, args...);
}


void fio() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

}


void solve() {
    int n,m,d;
    cin>>n>>m>>d;
    int size=n*m;
    vin(v,size);
    sort(all(v));
    rep(i,1,size){
        if((v[i]-v[i-1])%d){
            cout<<-1;
            return;
        }
    }
    int cnt=0;
    if(size&1){
        int idx=size/2;
        rep(i,0,size) cnt+=abs(v[idx]-v[i])/d;
    }
    else{
        int i1=size/2,i2=size/2-1;
        int c1=0,c2=0;
        rep(i,0,size) c1+=abs(v[i1]-v[i])/d;
        rep(i,0,size) c2+=abs(v[i2]-v[i])/d;
        cnt=min(c1,c2);
    }
    cout<<cnt;
}


int32_t main()
{
	fio();
	// clock_t z = clock();
	// w(t)
	solve();
	// cerr << "Run Time : " << ((double)(clock() - z) / CLOCKS_PER_SEC);
	return 0;
}