foo.c: In function ‘main’:
foo.c:8:9: warning: unused variable ‘i’ [-Wunused-variable]
    8 |     int i;
      |         ^
foo.c:6:17: warning: unused variable ‘tot’ [-Wunused-variable]
    6 |         int num,tot=0;
      |                 ^~~
foo.c: In function ‘judge_su’:
foo.c:17:5: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
   17 |     if (num==1)
      |     ^~
foo.c:19:9: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’
   19 |         for(i=2;i<num;i++)
      |         ^~~