UVa 12485 - Perfect Choir Solution

#include<iostream>
#include<cstdio>
#include<list>
#include<string>
#include<cstring>
#include<sstream>
#include<cctype>
#include<string.h>
#include<algorithm>
#include<cmath>
#include<stack>
#include<fstream>
#include<cstdlib>
#include<vector>
#include<map>
#include<set>
#include<utility>
#include<iomanip>
#include<queue>
#include<iterator>
#include<assert.h>

using namespace std;

#define INF (1<<63)-1
#define SET(a) memset(a,-1,sizeof(a))
#define ALL(a) a.begin(),a.end()
#define CLR(a) memset(a,0,sizeof(a))
#define PB push_back
#define FOR(i,n) for(int i = 0;i<n;i++)
#define PI acos(-1.0)
#define EPS 1e-9
#define MP(a,b) make_pair(a,b)
#define min3(a,b,c) min(a,min(b,c))
#define max3(a,b,c) max(a,max(b,c))
#define READ freopen("input.txt", "r", stdin)
#define WRITE freopen("output.txt", "w", stdout)
#define LL long long
#define MOD 1000000007
#define S(a) scanf("%d",&a)
#define P(a) printf("%d",a)
#define KS printf("Case %d: ",kk++)
#define NL printf("\n")
#define MX 100000



int main()
{
int n,arr[MX];
string s;
while(cin>>n)
{
    int sum=0;
    FOR(i,n)
        {
            cin>>arr[i];
            sum+=arr[i];
        }

    if(sum%n)
        cout<<"-1"<<endl;
    else
    {
        sum/=n;
        int cnt=1;
        int pos=0;
        while(arr[pos]<sum)
        {
            cnt+=(sum-arr[pos]);
            pos++;
        }
        cout<<cnt<<endl;
    }


}
return 0;
}