/tmp/ccD8j63t.o: In function `main':
foo.cc:(.text.startup+0xc4): undefined reference to `lcm(int, int)'
foo.cc:(.text.startup+0x1b6): undefined reference to `gcd(int, int)'
foo.cc:(.text.startup+0x1d7): undefined reference to `Output(int, int)'
collect2: error: ld returned 1 exit status