谁能帮我挑挑错误啊。

//找出文件中不含有字母dfpg的单词中最长单词

#include"stdafx.h"
#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
using namespace std;
int main()
{
ifstream input("E:\\pro.txt");
if (!input)
{
cerr << "error!" << endl;
return -1;
}
string line;
istringstream record;
string word;
string s0 = "dfpg";
string longest;
int len;

while (getline(input, line))
{
record.str(line);
while (record >> word)
if (word.find_first_of(s0) == string::npos)
word.size() > longest.size() ? longest = word :longest=longest ;


}
cout << longest;
return 0;
}

我的这段代码问题在哪