Compilare: user.cpp: In function ‘int main()’: user.cpp:50:16: warning: left operand of comma operator has no effect [-Wunused-value] for(i, j; i <= n && j <= m ; ++j, ++i){ ^ user.cpp:50:17: warning: right operand of comma operator has no effect [-Wunused-value] for(i, j; i <= n && j <= m ; ++j, ++i){ ^ user.cpp:59:16: warning: left operand of comma operator has no effect [-Wunused-value] for(i, j; i <= n && j <= m ; ++j, ++i){ ^ user.cpp:59:17: warning: right operand of comma operator has no effect [-Wunused-value] for(i, j; i <= n && j <= m ; ++j, ++i){ ^ user.cpp:33:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("submatrix.in", "r", stdin); ^ user.cpp:34:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("submatrix.out", "w", stdout); ^ user.cpp:35:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &n, &m, &k); ^ user.cpp:39:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i][j]); ^