/in/foo.c: In function 'main':
/in/foo.c:13:8: warning: implicit declaration of function 'gcd' [-Wimplicit-function-declaration]
      m=gcd(arr[i],arr[i+1]);
        ^~~
/in/foo.c:16:4: warning: 'm' may be used uninitialized in this function [-Wmaybe-uninitialized]
    printf("%d",m);
    ^~~~~~~~~~~~~~