#include<stdio.h>
int mod(int n,int m)
{
   if(n<m)   
     return n;
   else
     {
            
     int c=n/m;       
     return n-c*m;       
            
     } 
    }
void main()
{
     
int a,b;     
while(scanf("%d %d",&a,&b)!=EOF)     
      printf("%d\n",mod(a,b));  
 
     
     
     
     
     
     
     
  }