Main.cc: In function 'int main()':
Main.cc:8:19: error: 'a' was not declared in this scope
scanf("%d",&a[i][j]);
^
Main.cc:12:3: error: 'sum' was not declared in this scope
sum=0;
^
Main.cc:14:7: error: 'a' was not declared in this scope
if(a[i][j]==1)sum++;
^
Main.cc:5:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d",&n);
^