//cau 1:
//cach 1:
//#include <stdio.h>
//int main() {
//    int a[1000], n;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) scanf_s("%d", &a[i]);
//    return 0;
//}
//cach 2: 
//#include <stdio.h>
//#include <stdlib.h>
//#include <time.h>
//
//int main() {
//    int a[1000], n;
//    scanf_s("%d", &n);
//    srand((unsigned)time(NULL));
//    for (int i = 0; i < n; i++) a[i] = rand() % 201 - 100;
//    return 0;
//}
//=======================================================================
//cau 2:
//#include <stdio.h>
//int main() {
//    int a[1000], n;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) scanf_s("%d", &a[i]);
//    for (int i = 0; i < n; i++) printf("%d ", a[i]);
//    return 0;
//}
//=========================================================================
//cau 3:
//#include <stdio.h>
//int main() {
//    int a[1000], n, s = 0;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) { scanf_s("%d", &a[i]); s += a[i]; }
//    printf("%.3lf", (double)s / n);
//    return 0;
//}
//================================================================================
//bai 4: 
//#include <stdio.h>
//int main() {
//    int a[1000], n;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) scanf_s("%d", &a[i]);
//    for (int i = 0; i < n; i += 2) printf("%d ", a[i]);
//    return 0;
//}
//=====================================================================================
//bai 5:
//#include <stdio.h>
//int main() {
//    int a[1000], n, c = 0;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) {
//        scanf_s("%d", &a[i]);
//        if (a[i] > 0) c++;
//    }
//    printf("%d", c);
//    return 0;
//}
//===================================================================================
//bai 6: 
//#include <stdio.h>
//int main() {
//    int a[1000], n, x, c = 0;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) scanf_s("%d", &a[i]);
//    scanf_s("%d", &x);
//    for (int i = 0; i < n; i++) if (a[i] == x) c++;
//    printf("%d", c);
//    return 0;
//}
//=============================================================================
//bai 7: 
//#include <stdio.h>
//int main() {
//    int a[1000], n, x;
//    scanf_s("%d", &n);
//    for (int i = 0; i < n; i++) scanf_s("%d", &a[i]);
//    scanf_s("%d", &x);
//    for (int i = 0; i < n; i++) if (a[i] == x) { printf("%d", i); return 0; }
//    printf("-1");
//    return 0;
//}