C :

#include <stdio.h>
#include <math.h>
int main ()
{
 int a,b,c;
 scanf("%d%d",&a,&b);
 c=a%b;
 printf("%d",c);
 return 0;
}

C++ :

#include "stdio.h"
#define qiuyu(a,b) a%=b;
int main(int argc, char* argv[])
{ 
	int a,b;
  while(~scanf("%d%d",&a,&b))
  {
   qiuyu(a,b);
   printf("%d\n",a);
  }  
	return 0;
}