foo.cc: In function ‘int main()’:
foo.cc:4:12: warning: unused variable ‘a’ [-Wunused-variable]
    4 | {int n,t,s,a,b,sum;
      |            ^
foo.cc:4:14: warning: unused variable ‘b’ [-Wunused-variable]
    4 | {int n,t,s,a,b,sum;
      |              ^