It works in my computer 0k...

#include<iostream>
#include<string.h>
#include<cstdio>
#include<vector>
#include<cmath>
using namespace std;
int main(){
        unsigned long long aux;
        vector<unsigned long long>v1;
        while(cin >> aux)v1.push_back(aux);
        int i=v1.size()-1;
        while(i>=0){
                printf("%.4f\n",sqrt(v1[i]));
                i--;
        }
}

cb37c1a6-2f8c-4b8d-9b35-bb945448c8b1
cb37c1a6-2f8c-4b8d-9b35-bb945448c8b1(14) : error C2668: 'sqrt' : ambiguous call to overloaded function
        S:\checker\compile\vc10\include\math.h(589): could be 'long double sqrt(long double)'
        S:\checker\compile\vc10\include\math.h(541): or       'float sqrt(float)'
        S:\checker\compile\vc10\include\math.h(127): or       'double sqrt(double)'
        while trying to match the argument list '(unsigned __int64)'

Just make vector of doubles. Everything will be OK.

Error because function sqrt() gets double or long double or float parameter.