friends.cpp: In function 'int main()':
friends.cpp:56:39: warning: comparison of integer expressions of different signedness: 'std::vector<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
56 | if((l==0 && s[0]==s[n-1])||(a.size()!=n/2)||(s[n/2]==s[0] && s[n/2]==s[n/2+1]&& s[n/2]!=s[n-1] && l==0)||y==0){
| ~~~~~~~~^~~~~
friends.cpp:60:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
60 | for(int i=0;i<a.size();i++){
| ~^~~~~~~~~
friends.cpp:19:7: warning: unused variable 'us' [-Wunused-variable]
19 | int us=-1;
| ^~
friends.cpp:21:7: warning: unused variable 'x' [-Wunused-variable]
21 | int x,y;
| ^
friends.cpp:21:9: warning: unused variable 'y' [-Wunused-variable]
21 | int x,y;
| ^