I am getiing wa in two test case and one test case got cleared what is wa and how can I eradicate it?

#include

#include

#include

using namespace std;

int bintodec(string n)

{

string num = n;

int dec_value = 0;

```
// Initializing base value to 1, i.e 2^0
int base = 1;
int len = num.length();
for (int i = len - 1; i >= 0; i--) {
if (num[i] == '1')
dec_value += base;
base = base * 2;
}
return dec_value;
```

}

int main() {

int f;

cin>>f;

while(f!=0)

{

string a,b;

cin>>a>>b;

int count=0;

int c=bintodec(a);

int d=bintodec(b);

while(d!=0)

{

int u=c^d;

int v=c&d;

c=u;

d=v*2;

count+=1;

}

cout<<count<<endl;

fโ;

}

// your code goes here

return 0;

}