foo.c: In function 'main':
foo.c:6:9: warning: too many arguments for format [-Wformat-extra-args]
  printf("请输入一个正整数:\n",a);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:15:5: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
     else
     ^~~~
foo.c:17:2: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'else'
  return 0;
  ^~~~~~
foo.c:7:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&a);
     ^~~~~~~~~~~~~~
foo.c:6:2: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  printf("请输入一个正整数:\n",a);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:8:7: warning: 'c' is used uninitialized in this function [-Wuninitialized]
  while(c!=0)
       ^

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