#include <cstdio>

int ncall;
int call[100];

void solve(int K)
{
    if (!K) return;

    if (K % 2 == 0) {
        call[ncall] = ++ncall;
        if (K > 2) solve(K / 2);
    } else {
        call[ncall++] = -1;
        solve(K - 1);
    }
}

int main( void )
{
//    freopen( "p1278.in", "r", stdin );

    int K;
    scanf( "%d", &K );

    if (K > 1) solve(K);
    for (int i = 0; i < ncall; i++)
        printf( "CALL %d\n", call[i] < 0 ? ncall : call[i] );
    printf( "BELL&RET\n" );

    return 0;
}

For test #1, K = 4, and my code output:
CALL 1
CALL 2
BELL&RET
I think it's correct.

хз