/in/foo.cc:21:9: error: redefinition of 'int a [20]'
 int a[20],m=0,n=0;
         ^
/in/foo.cc:4:5: note: 'int a [20]' previously declared here
 int a[20],m=0,n=0;
     ^
/in/foo.cc:21:11: error: redefinition of 'int m'
 int a[20],m=0,n=0;
           ^
/in/foo.cc:4:11: note: 'int m' previously defined here
 int a[20],m=0,n=0;
           ^
/in/foo.cc:21:15: error: redefinition of 'int n'
 int a[20],m=0,n=0;
               ^
/in/foo.cc:4:15: note: 'int n' previously defined here
 int a[20],m=0,n=0;
               ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:23:5: error: redefinition of 'int main()'
 int main(){
     ^~~~
/in/foo.cc:6:5: note: 'int main()' previously defined here
 int main(){
     ^~~~