Compilare: user.cpp: In function ‘void build(int, int, int)’: user.cpp:55:54: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0, j = 0; i < sgt[nd << 1].lst.size() || j < sgt[nd << 1 | 1].lst.size(); ) { ^ user.cpp:55:89: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0, j = 0; i < sgt[nd << 1].lst.size() || j < sgt[nd << 1 | 1].lst.size(); ) { ^ user.cpp:56:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == sgt[nd << 1].lst.size()) ^ user.cpp:59:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (j == sgt[nd << 1 | 1].lst.size()) ^ user.cpp:67:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (mnl < sgt[nd << 1].lst.size() && sgt[nd << 1].lst[mnl].y < sgt[nd].lst.back().y) ++mnl; ^ user.cpp:68:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (mnr < sgt[nd << 1 | 1].lst.size() && sgt[nd << 1 | 1].lst[mnr].y < sgt[nd].lst.back().y) ++mnr; ^ user.cpp:70:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (mxl + 1 < sgt[nd << 1].lst.size() && sgt[nd << 1].lst[mxl + 1].y <= sgt[nd].lst.back().y) ++mxl; ^ user.cpp:71:52: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (mxr + 1 < sgt[nd << 1 | 1].lst.size() && sgt[nd << 1 | 1].lst[mxr + 1].y <= sgt[nd].lst.back().y) ++mxr; ^ user.cpp: In function ‘int main()’: user.cpp:172:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("h.in" , "r", stdin ); ^ user.cpp:173:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("h.out", "w", stdout); ^ user.cpp:179:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:182:61: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &sgm[i].x, &sgm[i].y1, &sgm[i].y2); ^