no.4

#include<stdio.h>
int main()
{
    long v,t;
    while(scanf("%ld%ld",&v,&t)==2)
      printf("%ld\n",2*v*t);
return 0;
}

两个数相乘的2倍就ok了

转载于:https://www.cnblogs.com/lovewzh/archive/2013/02/25/wangze.html