/in/ex3.cpp:3:19: error: extra ';' [-Werror=pedantic]
 int main(){ex4();};
                   ^
/in/ex3.cpp: In function 'void ex4()':
/in/ex3.cpp:18:18: error: ISO C++ forbids variable length array 'mat1' [-Werror=vla]
     int mat1[n][n],mat2[n][n],mataplusb[n][n],matab[n][n],matatbt[n][n];
                  ^
/in/ex3.cpp:18:18: error: ISO C++ forbids variable length array 'mat1' [-Werror=vla]
/in/ex3.cpp:18:29: error: ISO C++ forbids variable length array 'mat2' [-Werror=vla]
     int mat1[n][n],mat2[n][n],mataplusb[n][n],matab[n][n],matatbt[n][n];
                             ^
/in/ex3.cpp:18:29: error: ISO C++ forbids variable length array 'mat2' [-Werror=vla]
/in/ex3.cpp:18:45: error: ISO C++ forbids variable length array 'mataplusb' [-Werror=vla]
     int mat1[n][n],mat2[n][n],mataplusb[n][n],matab[n][n],matatbt[n][n];
                                             ^
/in/ex3.cpp:18:45: error: ISO C++ forbids variable length array 'mataplusb' [-Werror=vla]
/in/ex3.cpp:18:57: error: ISO C++ forbids variable length array 'matab' [-Werror=vla]
     int mat1[n][n],mat2[n][n],mataplusb[n][n],matab[n][n],matatbt[n][n];
                                                         ^
/in/ex3.cpp:18:57: error: ISO C++ forbids variable length array 'matab' [-Werror=vla]
/in/ex3.cpp:18:71: error: ISO C++ forbids variable length array 'matatbt' [-Werror=vla]
     int mat1[n][n],mat2[n][n],mataplusb[n][n],matab[n][n],matatbt[n][n];
                                                                       ^
/in/ex3.cpp:18:71: error: ISO C++ forbids variable length array 'matatbt' [-Werror=vla]
cc1plus: all warnings being treated as errors