/in/foo.cc: In function 'int main()':
/in/foo.cc:12:35: warning: format '%d' expects argument of type 'int*', but argument 3 has type 'int' [-Wformat=]
   scanf("%d %d", &a[i][0], a[i][1]);
                                   ^
/in/foo.cc:7:9: warning: 'n' is used uninitialized in this function [-Wuninitialized]
  int a[n+10][3];
        ~^~~
/in/foo.cc:34:20: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
   printf("%d\n", c);
                    ^
/in/foo.cc:22:7: warning: 'v' may be used uninitialized in this function [-Wmaybe-uninitialized]
     v -= a[i][0];
     ~~^~~~~~~~~~