foo.cpp: In function 'void record(int, int)':
foo.cpp:52:32: warning: unused variable 'b1' [-Wunused-variable]
  int num1=num[n1],num2=num[n2],b1=b[n1],b2=b[n2],b3=max(b[n1],b[n2]);
                                ^
foo.cpp:52:41: warning: unused variable 'b2' [-Wunused-variable]
  int num1=num[n1],num2=num[n2],b1=b[n1],b2=b[n2],b3=max(b[n1],b[n2]);
                                         ^
foo.cpp: In function 'void input()':
foo.cpp:97:11: error: 'exit' was not declared in this scope
     exit(0);
           ^