View Compilation Error

0_0_18302575_8090.cpp: In function 'int main()':
0_0_18302575_8090.cpp:40:9: error: 'i' was not declared in this scope
     for(i=0;i<=(n+1)/2;i++)
         ^
0_0_18302575_8090.cpp:49:21: error: 'a' was not declared in this scope
                     a[i][j]=op;
                     ^
0_0_18302575_8090.cpp:53:21: error: 'a' was not declared in this scope
                     a[k][n-i-1]=op;
                     ^
0_0_18302575_8090.cpp:57:21: error: 'a' was not declared in this scope
                     a[n-1-i][l]=op;
                     ^
0_0_18302575_8090.cpp:61:21: error: 'a' was not declared in this scope
                     a[m][i]=op;
                     ^