/in/foo.cc:5:1: error: 'string' does not name a type
 string s,c;
 ^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:10:1: error: 'cin' was not declared in this scope
 cin>>n;
 ^~~
/in/foo.cc:12:13: error: 's' was not declared in this scope
 getline(cin,s);
             ^
/in/foo.cc:13:1: error: 'c' was not declared in this scope
 c=s;
 ^
/in/foo.cc:19:1: error: 'cout' was not declared in this scope
 cout<<n-a[n][n];
 ^~~~