/in/foo.c: In function 'main':
/in/foo.c:11:9: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[20]' [-Wformat=]
 scanf("%s %d %d %c %c %d",&c1,&a,&b,&c,&d,&e);
         ^
/in/foo.c:28:2: warning: implicit declaration of function 'strcpy' [-Wimplicit-function-declaration]
  strcpy(c2,c1);
  ^~~~~~
/in/foo.c:28:2: warning: incompatible implicit declaration of built-in function 'strcpy'
/in/foo.c:28:2: note: include '<string.h>' or provide a declaration of 'strcpy'
/in/foo.c:7:25: warning: unused variable 'c3' [-Wunused-variable]
 char c1[20];char c2[20],c3[20];
                         ^~
/in/foo.c:36:1: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
 printf("%s\n%d\n%d\n",c2,f[max],s);
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~