How to get it working if I use n in for it works but I used r and got it printed but no digits

Can someone help me? I can't figure out where its wrong with. The program stops working if I change the 'n' to 'r' in for but if its 'n' it works just fine but there aren't any digits/results that appear.

include

    float avg;

    float t1[5],t2[5],t3[5],h1[5],h2[5],h3[5],h4[5],pj[5];
    float t[5],h[5],prj[5],mark[5],sum=0;
    char *grade[10], *overall;
    char a[10];
    int n,r;
    int student[10];
    int Ap=0,A=0,Am=0,Bp=0,B=0,Bm=0,Cp=0,C=0,Cm=0,F=0;

    for (r=1;r<=68;++r){

fscanf(f1,"%f%f%f%f%f%f%f%f\n",&t1[r],&t2[r],&t3[r],&h1[r],&h2[r],&h3[r],&h4[r],&pj[r]);

   t[r]=(t1[r]+t2[r]+t3[r])*20/100;
   h[r]=(h1[r]+h2[r]+h3[r]+h4[r])*10/40;
   prj[r]=pj[r]*30/100;
   mark[r]=t[r]+h[r]+prj[r];

   sum= sum+mark[r];    
   }

   for (r=1;r<=68;++r)
   if (mark[r]>=90){
   grade[r]="A+";
   Ap+=1;
   }
   else if (mark[r]>=80){
   grade[r]="A";
   A+=1;
   }
   else if (mark[r]>=70){
   grade[r]="A-";
   Am+=1;

   for (r=1;r<=68;++r)
   {
   student[r]=r;
   printf(" %3d Student%3d  ID%3d   %.1f    %3s\n",student[r],student[r],student[r],mark[student[r]],grade[student[r]]);
}
   printf("\nGrade Distribution of the Students : \n");
   printf("\nA+ : %d \n",Ap);
   printf("\nA : %d \n",A);
   printf("\nA- : %d \n",Am);

}