#include <stdio.h>
#include <stdlib.h>

int doub(int);
int trip(int);
int half(int);
void fpv_exec(int (**)(int), int);

int doub(int i) {
    return i * 2;
}

int trip(int i) {
    return i * 3;
}

int half(int i) {
    return i / 2;
}

static int (*fpv[])(int) = {doub, trip, half, NULL};

void fpv_exec(int (**fpv)(int), int n) {
    int i;
    for (i = 0; *(fpv + i) != NULL; i++) {
        printf("%d\n", (*(fpv + i))(n));
    }
}

int main(int argc, char **argv) {
    int i;
    for (i = 1; i < argc; i++) {
        fpv_exec(fpv, atoi(argv[i]));
    }

    exit(EXIT_SUCCESS);
}