College take no. Of groups of students as(N) and students has to get in a hyperloop which has single (S)or double (D)seat pod.

Question

if a group consist of one person it uses S if none of the S is not available then use D and still none available then student service of hyperloop denied that has to be obtained output .the following is the test case :-
input-4 1 2 //here 4 is no. of groups
1 2 1 1 //4 groups having students size
output-0 // no one is denied as 1+4"1+2×2"=1+2+1+1
input-4 1 1 // 1 S ,1 D
1 1 2 1
output-2 //2 will be denied as 1+1=! 1+1+2+1 2-5=-2 so the answer is 2