Compilare: main.cpp: In function 'void citire_matrice()': main.cpp:13:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= n; i++) { ~~^~~~ main.cpp:14:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j <= m; j++) { ~~^~~~ main.cpp: In function 'void back(int)': main.cpp:21:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k > n) { ~~^~~ main.cpp:23:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j <= m; j++) { ~~^~~~ main.cpp:25:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= n; i++) { ~~^~~~