(gdb) b MD.o.c:649 <-- Calc_gr
(gdb) b MD.o.c:671 <-- Calc_vacf
(gdb) r
Breakpoint 1, Calc_gr (particle=0x827dea0) at MD.o.c:649
(gdb) c
649      fclose(file_gr);
(gdb) p &j
$1 = (int *) 0xffffc168
(gdb) p j
$3 = 144
(gdb) c
Breakpoint 2, Calc_vacf () at MD.o.c:671
671         vacf[j-i]=0;
(gdb) p &j
$6 = (int *) 0xffffc168
(gdb) p j
$7 = 144