/in/foo.c:2:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main(){
 ^
/in/foo.c: In function 'main':
/in/foo.c:6:14: warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int' [-Wformat=]
  while(scanf("%d",a[i++])==1&&!(i==2*m-1)){
              ^