/*#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("Hello world!\n");
return 0;
}
*/
/*
#include<stdio.h>
int main()
{
float a;
float b;
scanf("%f %f", &a, &b);
printf("%.2f", a * b);
return 0;
}*/
/*
#include <stdio.h>
int main()
{
float a,b;
scanf("%f %f",&a,&b);
printf("%.1f",a*b/2);
return 0;
}
*/
#include <stdio.h>
int main()
{
int a,b;
scanf("%d %d",&a,&b);
printf("%d",a%b);
return 0;
}