Compilare: main.cpp: In function 'int main()': main.cpp:76:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (G[i].size() < k) ~~~~~~~~~~~~^~~ main.cpp:83:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (G[i].size() < k) ~~~~~~~~~~~~^~~ main.cpp:89:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (G[i].size() >= k) ~~~~~~~~~~~~^~~~ main.cpp:53:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("zone2.in", "r", stdin); ^ main.cpp:54:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("zone2.out", "w", stdout); ^ main.cpp:57:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &n, &m, &k); ^ main.cpp:59:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("\n"); ^ main.cpp:61:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%c", &c[i][j]); ^