/in/foo.c: In function 'main':
/in/foo.c:6:13: warning: comparison of constant '100' with boolean expression is always true [-Wbool-compare]
    6 |     if(80<=a<=100)
      |             ^~
/in/foo.c:6:10: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
    6 |     if(80<=a<=100)
      |        ~~^~~
/in/foo.c:8:18: warning: comparison of constant '79' with boolean expression is always true [-Wbool-compare]
    8 |     else if(70<=a<=79);
      |                  ^~
/in/foo.c:8:15: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
    8 |     else if(70<=a<=79);
      |             ~~^~~
/in/foo.c:8:10: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
    8 |     else if(70<=a<=79);
      |          ^~
/in/foo.c:9:5: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
    9 |     {printf("B");}
      |     ^
/in/foo.c:10:5: error: 'else' without a previous 'if'
   10 |     else if(60<=a<=69);
      |     ^~~~
/in/foo.c:10:18: warning: comparison of constant '69' with boolean expression is always true [-Wbool-compare]
   10 |     else if(60<=a<=69);
      |                  ^~
/in/foo.c:10:15: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
   10 |     else if(60<=a<=69);
      |             ~~^~~
/in/foo.c:10:10: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   10 |     else if(60<=a<=69);
      |          ^~
/in/foo.c:11:5: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   11 |     {printf("C");}
      |     ^
/in/foo.c:12:5: error: 'else' without a previous 'if'
   12 |     else {printf("D");}
      |     ^~~~