Please fix the code given below to perform subtraction of two inputs:
#include <stdio.h>
#include <stdlib.h>
int readNumber(); 
void $1(int number);
int main(int argc, char *argv[])
{
  
  int a, b;
  a = $2;
  b = $3;
  
  writeNumber($4);
  return 0;
}
void writeNumber(int number){
     printf("%d",number);
     return;
}
int readNumber(){
    int x;
    scanf("%d", &x);
    return x;    
}
 
Input 1
10 11
Output 1
10 11
-1
 
Input 2
90 12
Output 2 
90 12
78