程式碼：

#include<iostream>  
#include<string>  
using namespace std;  
int main()  
{  
    string sum(string s1,string s2);  
    string s1,s2;  
    cin>>s1>>s2;  
    cout<<sum(s1,s2)<<endl;  
    return 0;  
}  
string sum(string s1,string s2)   
{   
     if(s1.length()<s2.length())   
     {   
          string temp=s1;   
          s1=s2;   
          s2=temp;   
     }   
     for(int i=s1.length()-1,j=s2.length ()-1;i>=0;i--,j--)   
     {   
          s1[i]=char(s1[i]+(j>=0?s2[j]-'0':0));   
          if(s1[i]-'0'>=10)   
          {   
              s1[i]=char((s1[i]-'0')%10+'0');   
              if(i)   
                   s1[i-1]++;   
              else   
                   s1='1'+s1;   
          }   
     }   
     return s1;   
}