Compilare: user.cpp: In function ‘void solve()’: user.cpp:23:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < G[x].size(); i++) ^ user.cpp:34:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < G[y].size(); j++) ^ user.cpp: In function ‘void read_data()’: user.cpp:48:9: warning: unused variable ‘j’ [-Wunused-variable] int i, j, a, b; ^ user.cpp:49:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &N, &M, &X); ^ user.cpp:52:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &val[i]); ^ user.cpp:58:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &a, &b); ^ user.cpp: In function ‘int main()’: user.cpp:68:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("markon.in", "rt", stdin); ^ user.cpp:69:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("markon.out", "wt", stdout); ^