为什么只得了15分?求解

#include <iostream>
#include <cmath>
using namespace std;
int main ()
{    
int n ,sum = 0,a,b;    
int x = 0, k;    
cin >> n;    
for (int i = 1;i <= n;i++){        
cin >> k;        
a = k;        
b = k;        
while (k){            
k /= 10;            
++x;        
}        
while (a){            
int t = a % 10;            
sum =sum + pow (t, x);            
a /= 10;        
}           
if(sum == b){            
cout << "T"<<endl;        
}        
else{            
cout << "F"<<endl;        
}    
}    
return 0;
}