Main.cc: In function 'int main()':
Main.cc:10:9: error: 'n' was not declared in this scope
cin>>n[i][j];
^
Main.cc:17:7: error: 'n' was not declared in this scope
if(n[i][j]/100>=1)
^
Main.cc:21:7: error: 'n' was not declared in this scope
if(n[i][j]/10>=1)
^
Main.cc:5:6: warning: unused variable 'a' [-Wunused-variable]
int a[3][4];
^