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  1. #include <iostream>
  2. #include <cstdio>
  3. using namespace std;
  4.  
  5. int main() {
  6. int n, d, t, cnt=0;
  7. scanf("%d%d", &n, &d);
  8. while(n--) {
  9. scanf("%d", &t);
  10. d-=t;
  11. if(n) d-=10, cnt+=2;
  12. }
  13. if(d<0) printf("-1");
  14. else {
  15. cnt+=d/5;
  16. printf("%d", cnt);
  17. }
  18. return 0;
  19. }
Success #stdin #stdout 0s 3300KB
stdin
3 20
2 1 1
stdout
-1