Compilare: user.cpp: In function ‘int main()’: user.cpp:49:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (sol.size() - 1 != n) return fo << "0\n",0; ^ In file included from /usr/include/c++/4.8/cassert:43:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:33, from user.cpp:1: user.cpp:53:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i <= 9;++i) assert(pp[i] == v[i][i].size()); ^