include <math.h>
void findA(int *a, int temp, int index, int average, int n){
int i; if(temp == (-2)){ for(i = index+1; i< n ;){ if(a[i] <= average){ i++; continue; } else if( a[i] > average ){ a[i]-=2; temp = 0; return; } } } else if(temp == (2)){ for(i = index+1; i< n ;){ if(a[i] >= average){ i++; continue; } else if( a[i] < average ){ a[i]+=2; temp = 0; return; } } }
}
int greedyAlg(int *a, int average, int n){
int count=0;
int temp = 0;
int i = 0;
for( ; i<n ; ){
if(a[i]>average){
a[i]-=2;
temp = 2;
}
else if(a[i]<average){
a[i]+=2;
temp = -2;
}
else{
i++;
continue;
}
// printf("\ntemp = %d a[%d] = %d", temp, i, a[i]);
findA(a, temp, i, average, n);
count++;
}
return count;
}
int main(){
int n;
int *a;
int sum=0, i=0, count=0;
int average;
scanf("%d",&n); a = (int)malloc(n*sizeof(int)); while(i != n){ scanf("%d", a+i); sum += a[i]; i++; } // printf("%d\n", sum%n); if((sum % n) != 0){ printf("-1"); return 0; } average = sum/n; for(i=0; i<n; i++){ if(abs(a[i]-average)%2 == 1){ printf("-1"); return 0; } } printf("%d", greedyAlg(a, average, n)); free(a); return 0;
}