submatrix.cpp: In function 'int main()': submatrix.cpp:4: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result submatrix.cpp:5: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result submatrix.cpp:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result submatrix.cpp:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result submatrix.cpp:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result submatrix.cpp:6: warning: 'l1' may be used uninitialized in this function submatrix.cpp:6: warning: 'c2' may be used uninitialized in this function submatrix.cpp:6: warning: 'c1' may be used uninitialized in this function submatrix.cpp:6: warning: 'l2' may be used uninitialized in this function