#include  "calcmarks.h"    // local header file provides declarations

int main(int argc, char *argv[])
{
    int nmarks = 0;

//  IF WE RECEIVED NO COMMAND-LINE ARGUMENTS, READ THE MARKS FROM stdin
    if(argc == 1) {
         nmarks += readmarks(stdin);
    }
//  OTHERWISE WE ASSUME THAT EACH COMMAND-LINE ARGUMENT IS A FILE NAME
    else {
        for(int a=1 ; a<argc ; ++a) {
            FILE *fp = fopen(argv[a], "r");

            if(fp == NULL) {
                printf("Cannot open %s\n", argv[a]);  
                exit(EXIT_FAILURE);
            }
            nmarks += readmarks(fp);
//  CLOSE THE FILE THAT WE OPENED
            fclose(fp);
        }
    }
//  IF WE RECEIVED SOME MARKS, REPORT THEIR CORRELATION
    if(nmarks > 0) {
        correlation(nmarks);
    }
    return 0;
}