can anyone pls explain me why this code is not working for ques B. Decode String

while testing with the all 9 test cases(which is given in ques) this test case 5 11111 is giving me wrong ans while testing it separately it is giving the right ans

include<bits/stdc++.h>

using namespace std;

typedef long long li;

int main(){

li t;

cin>>t;

string ans="abcdefghijklmnopqrstuvwxyz";

while(t--){
   li n;
   cin>>n;
   string s;
   cin>>s;
   string res="";

   for(li i=0;i<s.length();i++){
    if( s[i+2]=='0' && s[i+3]!='0' && i<n){
           res+=ans[(s[i]-'0')*10+(s[i+1]-'0'-1)];
           i+=2;
   }else{
          res+=ans[s[i]-'0'-1];
      }
   }
   cout<<res<<endl;
}
return 0;

}