Regarding SIGTSTP error and unending input

The below code gives SIGTSTP but I am not able to find the fault. The original question link is: https://codeforces.com/contest/102/problem/B . Please Help.

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

  int main()
  {
    int x,sum=0,count=0;
    string s; cin>>s;


    while(s.length()>1){

      for(int i=0;i<s.length();i++){
        x=s[i]-'0';
        sum+=x;
      }
      s=std::to_string(sum);
      count++;
    }


    cout<<count;      
    return 0;
  }