#include <stdio.h>
#include<math.h>
int main(){
int m,t,s;
float apple;
scanf("%d %d %d",&m,&t,&s);
if(t==0){
apple=0;
}else{
 apple=((float)m-(float)s/t);
}
printf("%.0f",floor(apple));
return 0;
}