class Solution {
public:
    static int rec(string &s,int i=0){
    if(i==s.size()) return 1;
    if(s[i]=='0') return 0;
    string s1="50";
    if(i+2 <= s.size()) s1 = s.substr(i,2);
    int ans1 =0;
    int ans2= rec(s,i+1);
    if(stoi(s1) >0 && stoi(s1) <=26){
        ans1 = rec(s,i+2);
    }
    return ans1+ans2;
}

    int numDecodings(string s) {
    return rec(s);
    }
};