/* package whatever; // don't place package name! */
import java.util.*;
import java.lang.*;
class spoj
{
// this method takes number of packets in count variable and number of candies in each packet in input array.
void calculateMoves(int packet,int input[]){
int sum=0;
int candyPerPack=0;
int moves=0;
int j=0;
// sum all the candies available in each packet
for(j=0;j<packet;j++){
sum=sum+input[j];
}
// check whether the sum can be divided by number of packets or not.
// if not then print -1.
// else count how many candies need to be moved.
if((sum%packet)!=0){
}
else{
candyPerPack=sum/packet;
for(j=0;j<packet;j++){
if(input[j]<candyPerPack){
moves=moves+(candyPerPack-input[j]);
}
}
}
}
{
int input[]=new int[1000];
Scanner s
=new Scanner
(System.
in); int count=0;
spoj sp=new spoj();
int i=0,j=0;
int temp=0;
while(s.hasNext()){
count=s.nextInt();
if(count==-1){
break;
}
i=0;
while(i!=count){
input[i]=s.nextInt();
i++;
}
sp.calculateMoves(count,input);
}
}
}
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