Compilare: main.cpp: In function 'void inm(matrix&, matrix&, matrix&)': main.cpp:39:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0; k<B.size(); ++k) ~^~~~~~~~~ main.cpp:40:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<A.size(); ++i) ~^~~~~~~~~ main.cpp:41:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<B[0].size(); ++j) ~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:107:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("power.in", "r", stdin); ^ main.cpp:108:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("power.out", "w", stdout); ^