7-17 爬动的蠕虫

#include <stdio.h>
int main()
{
    int n,d,u,t=0,s=0;
    scanf("%d %d %d",&n,&d,&u);
    while(1)
    {
        t++;
        s+=d;
        if(s>=n)
            break;
        t++;
        s-=u;
    }
    printf("%d",t);
    return 0;
}