Compilare: In file included from /usr/include/c++/6/cassert:44:0, from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:33, from main.cpp:1: main.cpp: In function 'int main()': main.cpp:63:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] assert(mat[0].size() == n); ~~~~~~~~~~~~~~^~~~ main.cpp:64:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] assert(mat[1].size() == n); ~~~~~~~~~~~~~~^~~~ main.cpp:65:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] assert(mat[2].size() == n); ~~~~~~~~~~~~~~^~~~