View Compilation Error

0_0_23723698_18918.cpp: In function 'int main()':
0_0_23723698_18918.cpp:20:41: error: invalid conversion from 'int*' to 'int' [-fpermissive]
             maxz=G[i][i+a]+G[i+a][n-i-1]+G[n-i-a-1]
                                         ^
0_0_23723698_18918.cpp:21:13: error: expected ';' before 'minstep'
             minstep=min(step,col-step-1);
             ^
0_0_23723698_18918.cpp:22:33: error: 'col' was not declared in this scope
             for(int step=1;step<col;step++){
                                 ^