C :

#include<stdio.h>
#define x(a,b) a%b
int main()
{
    int n,a;
    scanf("%d%d",&n,&a);
    printf("%d\n",x(n,a));
    return 0;
}

C++ :

#include<cstdio>
#include<iostream>
using namespace std;
int main()
{
  int m,n;
  cin>>m>>n;
  int x=m%n;
  cout<<x<<endl;
}

Pascal :

var a,b:longint;
begin
  readln(a,b);
  writeln(a mod b);
end.