foo.c: In function 'main':
foo.c:6:2: warning: statement with no effect [-Wunused-value]
  for(xmin;xmin<=xmax;xmin++){
  ^~~
foo.c:4:17: warning: unused variable 'c' [-Wunused-variable]
  {int xmin,xmax,c;int sum=0;
                 ^
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d",&xmin,&xmax);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务