#include <bits/stdc++.h> 

using namespace std;

#define rep(i,n) for(int (i)=0;(i)<n;(i)++)
#define rep1(i,n) for(int (i)=1;(i)<=n;(i)++)
#define repU(i,bottom,ceiling) for(int (i)=(bottom);(i)<=(ceiling);(i)++)
#define repD(i,ceiling,bottom) for(int (i)=(ceiling);(i)>=(bottom);(i)--)
#define pub push_back
#define pob pop_back
#define prf printf
#define scf scanf
#define vci(v) for(int i=0;i<v.size();i++) cin>>v[i]
#define vco(v) for(int i=0;i<v.size();i++){ cout<<v[i]<<' '; } cout<<endl
#define mp make_pair
#define fir first
#define sec second
#define clr(arr) memset((arr),0,sizeof(arr))

typedef long long int ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<double> vdb;
typedef vector<vector<double>> vvdb;
typedef vector<long long int> vll;
typedef vector<vector<long long int>> vvll;
typedef pair<int,int> pii;

const string alphabet("abcdefghijklmnopqrstuvwxyz");
const vector<pair<int,int>> dir={{1,0},{0,1},{-1,0},{0,-1},{1,1},{-1,1},{-1,-1},{1,-1}};
const long double Pi=3.141592653589793238462643383279502884197;
const long double Napier=2.71828182845904523536;
const int Inf=(int)2e9+1e8;
const int Mod=(int)998244353;

template<typename T,typename U>                                                   
inline pair<T,U> operator+(const pair<T,U> & l,const pair<T,U> & r) {   
    return {l.fir+r.fir,l.sec+r.sec};                                    
} 

template<typename T,typename U> 
inline pair<T,U> operator-(const pair<T,U> & l,const pair<T,U> & r) {   
    return {l.fir-r.fir,l.sec-r.sec};                                    
} 

template<typename T,typename U>                                                   
inline pair<T,U> operator*(const pair<T,U> & l,const pair<T,U> & r) {   
    return {l.fir*r.fir,l.sec*r.sec};                                    
}

template<typename T,typename U>                                                   
inline pair<T,U> operator/(const pair<T,U> & l,const pair<T,U> & r) {   
    return {l.fir/r.fir,l.sec/r.sec};                                    
}

template<typename T> inline void Swap(T *x,T *y){ T tem=*x; *x=*y; *y=tem; }

/*
int thre1,thre2;
vi v;

template<typename T> inline bool judge(T n){
	return (thre1<=v[n]&&thre2>=v[n]);
}

template<typename T> inline T BiS(T bottom,T ceiling,bool thretype){
	T upper=ceiling+thretype;
	T lower=bottom-(!thretype);
	while(upper-lower>1){
		T mid=(upper+lower)/2;
		if(judge(mid)) (thretype?lower:upper)=mid;
		else (thretype?upper:lower)=mid;
	}
	return (thretype?lower:upper);
}
*/

/* The main code follows below */

inline int Power(int n,int e,int mod){
	long long res=1;
	long long pow=n;
	while(e){
		if(e&1) res=(res*pow)%mod;
		pow=(pow*pow)%mod;
		e>>=1;
	}
	return res;
}

int Rev[300003],Stair[300003];

inline int Comb(int n,int r,int mod){
	if(n<r||min(n,r)<0) return 0;
	return ((ll)Stair[n]*Rev[r])%mod;
}

int N,A,B;
ll K;

inline int Sum(int n){
	int sum=0;
	while(n){
		sum+=n%10;
		n/=10;
	}
	return sum;
}

inline void solve(){
	if(Sum(N)==1) cout<<10<<endl;
	else cout<<Sum(N)<<endl;
	return;
}

inline void input(){
	cin>>N;
	return;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	input();
	solve();
	return 0;
}

Measured memory_bytes: 256