P93

# include<bits/stdc++.h>
using namespace std;

const int N = 10000;
string str;
int f[N];

//f[i]表示以str[i]结尾的编码所能表示的字母序列个数
//f[i] = f[i-1] + f[i-2]  

int main()
{
    cin>>str;
    str = " "+str;
    f[0] = 1;
    f[1] = 1;
    for(int i = 2; i<str.length(); i++)
    {
        int a = int(str[i-1]-'0');
        int b = int(str[i]-'0');
        if(b>=1 && b<=26) f[i] += f[i-1];
        if(a!=0  && (a*10+b)>=1 && (a*10+b)<=26) f[i] += f[i-2];
    }
    cout<<f[str.length()-1]<<endl;
}