Main.c: In function 'mian':
Main.c:4:13: warning: implicit declaration of function 'power' [-Wimplicit-function-declaration]
    4 | double sum=(power(2,64)-1);
      |             ^~~~~
Main.c:8:1: warning: control reaches end of non-void function [-Wreturn-type]
    8 | }
      | ^
/usr/lib/gcc/x86_64-alpine-linux-musl/12.2.1/../../../../x86_64-alpine-linux-musl/bin/ld: /usr/lib/gcc/x86_64-alpine-linux-musl/12.2.1/../../../../lib/crt1.o: in function `_start_c':
/home/buildozer/aports/main/musl/src/1.2.4/crt/crt1.c:18: undefined reference to `main'
/usr/lib/gcc/x86_64-alpine-linux-musl/12.2.1/../../../../x86_64-alpine-linux-musl/bin/ld: /tmp/ccMbOcNj.o: in function `mian':
Main.c:(.text+0x19): undefined reference to `power'
collect2: error: ld returned 1 exit status