/in/foo.c: In function 'main':
/in/foo.c:8:4: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
  x=abs(n);
    ^~~
/in/foo.c:5:16: warning: unused variable 'sum' [-Wunused-variable]
  int n,x,i,m=1,sum=0;
                ^~~
/in/foo.c:5:12: warning: unused variable 'm' [-Wunused-variable]
  int n,x,i,m=1,sum=0;
            ^