十年oi一场空，不开longlong见祖宗

开了longlong还不够，计算顺序分先后

拿int乘int的时候，记得用longlong转存一步

50pts

long long sum[500005];
.........
sum[i]=sum[i-1]+(b[i].val-ht)*wd;

100pts

sum[i]=b[i].val-ht;
sum[i]=sum[i-1]+sum[i]*wd;

数据好水啊