/in/foo.c: In function 'main':
/in/foo.c:6:13: warning: unused variable 'b' [-Wunused-variable]
  int a[100],b[100];
             ^
/in/foo.c:5:12: warning: unused variable 'm' [-Wunused-variable]
  int i,j,n,m,t,sum;
            ^
/in/foo.c:28:3: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
   printf("%d",sum);
   ^~~~~~~~~~~~~~~~