#include <stdio.h>
int func(int n) {
    int a = -1;

    for (int i = 1; i <= n; i++) {
        a = 3 * a + 5;
    }

    return a;
}

int main(void) {
    int n = 3;
    printf("a%d = %d\n", n, func(n));
    return 0;
}