/in/foo.c: In function 'main':
/in/foo.c:5:11: warning: 'p' may be used uninitialized in this function [-Wmaybe-uninitialized]
 if (x=='2'||x=='3'||x=='7'||x=='8') p=0;
     ~~~~~~^~~~~~~~
/in/foo.c:10:10: note: 'p' was declared here
 char m,n,p;
          ^