void main() {
    int i;
    int num;    
    int ticks;
    int ticksAvg;
    
    num = 5;
    sonar_init();
    printf("press start \n");
    while(1) {   
        if(start_button()) {  
            ticksAvg = 0; 
            for(i=0; i<=num;) { 
                ticks = sonar() / num; 
                if(ticks > 0) { 
                    i += 1;
                    ticksAvg += ticks; 
                }
            }
            printf("ticks = %d\n", ticksAvg);
        }
    }
}