Program received signal SIGSEGV: Segmentation fault - invalid memory reference. Backtrace for this error: #0 0x7F68EFB57B57 #1 0x7F68EFB5815E #2 0x7F68EF06C8CF #3 0x40341B in sevta_ #4 0x405357 in rdcv_ #5 0x401FCC in MAIN__ at ex3_1.f:?