#include <stdio.h>
#include <stdlib.h>

int apply(int i, int (*f)(int));
int add5(int i);

int main(int argc, char *argv[])
{
  if (argc != 3) {
    fprintf(stderr,"Usage: %s number-file output-file\n",argv[0]);
    return 1;
  }
  
  FILE *fIn, *fOut;
  if ((fIn = fopen(argv[1],"r")) == NULL) {
    fprintf(stderr,"%s: Could not open %s for reading\n",argv[0], argv[1]);
    exit(2);     
  } else if ((fOut = fopen(argv[2],"w")) == NULL) {
    fprintf(stderr,"%s: Could not open %s for writing\n",argv[0], argv[2]);
    return 3;  
  } else {
    
    char input[128];
    char output[128];
    while (fgets(input, 128, fIn)) {
      sprintf(output,"%d\n",apply(atoi(input),&add5));
      fputs(output,fOut);
    }
    
    fclose(fIn);
    fclose(fOut);
  }   

  return 0;
}


int apply(int i, int (*f)(int))
{
  return (*f)(i);
}

int add5(int i)
{
  return i + 5;
}