Codeforces Beta Round #93 (Div. 2 Only) A题

这题，我弄了好久，就因为一个len=0.0未进行声明，导致我错了好几次！哎，无语了
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
int main()
{
int n,k,i,j;
double x[205],y[205],len;
cin>>n>>k;
for(i=0; i<n; i++)
{
cin>>x[i]>>y[i];
}
len=0.0;
for(i=0; i<n-1; i++)
{
len+=sqrt((x[i]-x[i+1])*(x[i]-x[i+1])+(y[i]-y[i+1])*(y[i]-y[i+1]));
}
len*=k;
len/=50;
printf("%0.9llf\n",len);
return 0;
}