dango3.cpp: In function 'void solve(std::vector<int>)':
dango3.cpp:23:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
23 | for(int i=0; i<a.size(); i++) used[i] = true;
| ~^~~~~~~~~
dango3.cpp:24:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
24 | for(int i=0; i<a.size(); i++) {
| ~^~~~~~~~~
dango3.cpp:26:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
26 | for(int j=0; j<a.size(); j++) {
| ~^~~~~~~~~