#include <stdio.h>

int foo(int n) {
    if (n>0) {
      return 2 * n - 1;
    } else {
      return - 2 * n;
    }

}

int main(void) {
    printf("%d -> %d\n",  1, foo(1));
    printf("%d -> %d\n", -1, foo(-1));
    printf("%d -> %d\n",  2, foo(2));
    printf("%d -> %d\n", -2, foo(-2));
    return 0;
}