n, k = (int(i) for i in input().split())
a = [int(i) for i in input().split()]
mi = min(a)
res = 0
for i in a:
d, r = divmod(i - mi, k)
if r == 0:
res += d
else:
res = -1
break
print(res)
#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main (){
ll n,k;
cin>>n>>k;
ll a[n];
for(ll i=0; i<n; i++){
cin>>a[i];
}
ll min = a[0];
for(ll i=0; i<n; i++){
if(a[i]<min) min=a[i];
}
ll count=0;
bool flag=true;
for(ll i=0; i<n; i++){
if(a[i]==min) continue;
else if((a[i]-min)%k==0){
count=count+((a[i]-min)/k);
}
else{
flag=false;
break;
}
}
if(flag==true) cout<<count;
else cout<<-1;
return 0;
}63A - Sinking Ship | 1704B - Luke is a Foodie |
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44A - Indian Summer | 1133C - Balanced Team |
1704A - Two 0-1 Sequences | 1467A - Wizard of Orz |
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215B - Olympic Medal | 1445A - Array Rearrangment |
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1291A - Even But Not Even | 1269A - Equation |
441A - Valera and Antique Items | 1702C - Train and Queries |
816B - Karen and Coffee | 838D - Airplane Arrangements |
148B - Escape | 847G - University Classes |