#include<stdio.h>
int CountDivisible(int value,int divisor){
    if(divisor==0){
        return 0;
    }
    int count=(value-1)/divisor;
    return count;
}
int main()
{
    int value,divisor;
    if(scanf("%d %d",&value,&value,&divisor)==2){
        int result=Countdivisible(value,divisor);
        printf("%d\n",result);
    }
    return 0;
}