Main.cc: In function 'int main()':
Main.cc:5:30: error: 'a' was not declared in this scope
scanf("%d %d %d %d", &t,&a,&b,&n);
^
Main.cc:5:33: error: 'b' was not declared in this scope
scanf("%d %d %d %d", &t,&a,&b,&n);
^