Compilare: main.cpp: In function 'void solve()': main.cpp:58:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i <= n && mt[i].size() > j && mt[i - 1].size() > j && mt[i - 1][j] == mt[i][j] && mt[i][j] == '1') ~~~~~~~~~~~~~^~~ main.cpp:58:64: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i <= n && mt[i].size() > j && mt[i - 1].size() > j && mt[i - 1][j] == mt[i][j] && mt[i][j] == '1') ~~~~~~~~~~~~~~~~~^~~