#include<cstdio>
#include<cmath>
 main()
{
	int m,t,s,b;
	double eaten;
	scanf("%d%d%d",&m,&t,&s);
	eaten = 1.0 * s / t;b = ceil(eaten);
	printf("%d",m - b);
	return 0;
}      

而且为什么：不用变量b，直接写printf("%d",m - ceil(eaten) ); 的话会输出0