/in/foo.c: In function 'main':
/in/foo.c:9:7: warning: statement with no effect [-Wunused-value]
   flag!=0;
   ~~~~^~~
/in/foo.c:3:16: warning: 'num' may be used uninitialized in this function [-Wmaybe-uninitialized]
 { int n,i,flag,num; 
                ^~~