C, pasted on Sep 16:
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 ``` ```#include #include #define MAX 100 void nhap (int a[], int &n) { do { printf("\nNhap so phan tu: "); scanf("%d", &n); if(n <= 0 || n > MAX) { printf("\nSo phan tu khong hop le. Xin kiem tra lai !"); } }while(n <= 0 || n > MAX); for(int i = 0; i < n; i++) { printf("\nNhap a[%d]: ", i); scanf("%d", &a[i]); } } void xuat(int a[], int n) { for(int i = 0; i < n; i++) { printf("%4d", a[i]); } } bool kiemtrahoanthien(int n) { int i = 1; int S = 0; while(i < n) { if(n % i == 0) { S = S + i; } i++; } if(S == n) return true; else return false; } int timvitrihoanthiencuoi(int a[], int n) { for(int i = n - 1; i >= 0; i--) { if(kiemtrahoanthien(a[i]) == true) { return i; } } return -1; } int main() { int n; int a[MAX]; nhap(a, n); xuat(a, n); int vitrihoanthiencuoi = timvitrihoanthiencuoi(a, n); printf("\nVi tri hoan thien cuoi la %d", vitrihoanthiencuoi); getch(); return 0; } ```

Output:
 ```1 2 3 4 5 6 7 8 9 10 11 ``` ```Line 17: error: conio.h: No such file or directory Line 5: error: expected ';', ',' or ')' before '&' token In function 'xuat': Line 25: error: 'for' loop initial declaration used outside C99 mode t.c: At top level: Line 31: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'kiemtrahoanthien' In function 'timvitrihoanthiencuoi': Line 51: error: 'for' loop initial declaration used outside C99 mode Line 53: error: 'true' undeclared (first use in this function) Line 53: error: (Each undeclared identifier is reported only once Line 53: error: for each function it appears in.) ```

#include<iostream>
using namespace std;
void Nhap(int n, int a[]){
for(int i=0; i<n; i++){
cout<<"a["<<i<<"]=";
cin>>a[i];
}
}
bool kt_sht(int n){
int t=0;
for (int i=1; i<=n/2; i++){
if (n%i==0) t+=i;
}
if(t==n) return true;
return false;
}
int vitri_sohoanthiencuoi(int n, int a[]){
for (int i=n-1; i>=0; i--){
if(kt_sht(a[i])){
return i;
break;
}
}
return -1;
}
int main(){
int n;
cout<<"Nhap so phan tu trong mang: ";
cin>>n;
int a[n];
Nhap(n,a);
cout<<endl<<vitri_sohoanthiencuoi(n,a)<<endl;
}