Can someone please tell me the problem with this code. It looks okay to me.
Environment: Linux, G++ C++11, GCC version 4.9.2

#include <cmath>
#include <iostream>
#include <iomanip>
#include <vector>
#include <sstream>
#include <ios>
#include <string>

using namespace std;

int main(void)
{
        vector<long long> v;

        string strBuf;
        long long result;
        while (getline(cin, strBuf)) {
                result = atoll(strBuf.c_str());
                v.push_back(result);
        }

        vector<long long>::reverse_iterator ritr = v.rbegin();
        while (ritr != v.rend()) {
                cout << fixed  << setprecision(4) << sqrtl(*ritr) << endl;
                ++ritr;
        }

        return 0;
}

Compilation:
$ g++ ktm_0_1.cpp -std=c++11

Sample execution seems fine to me:
$ ./a.out
 1427  0

   876652098643267843
5276538 <-- After this, I enter CTRL-D manually
2297.0716
936297014.1164
0.0000
37.7757