Q573: The Snail

/*
    注意:蝸牛不會爬負的，只有晚上會滑下去一個高度
    Run time: 0.000
*/
#include <stdio.h>

int main()
{
    double H, init, down, factor;
    double slide;
    double sum;
    double last;
    int day;
    while (scanf("%lf%lf%lf%lf", &H, &init, &down, &factor))
    {
        if (!H)   break;

        day = 1;
        sum = init;
        slide = init*(factor/100);
        last = init;

        while (true)
        {
            // morning
            if (sum > H)
            {
                printf("success on day %d\n", day);
                break;
            }

            // night
            sum -= down;
            if (sum < 0)
            {
                printf("failure on day %d\n", day);
                break;
            }

            day++;
            sum += last-slide;
            if (slide != init)
                last = last-slide;
        }
    }
    return 0;
}