/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
Standard output is empty
problem PP0501A, based on SPOJ submission 21979306 (C), 2018-07-12 22:09:26