string jia(string a1, string b1){
	string c1 = "";
	
	int a[505]={}, b[505]={}, c[505]={};
	int lena = a1.length();
	int lenb = b1.length();
	int lenc = max(lena, lenb);

	for(int i=0;i<lena;i++) a[i] = a1[lena-1-i]-'0';
	for(int i=0;i<lenb;i++) b[i] = b1[lenb-1-i]-'0';
	
	int x = 0;
	for(int i=0;i<lenc;i++){
		c[i] = a[i] + b[i] + x;
		x = c[i]/10;  // 计算进位情况 
		c[i] %= 10;   // 进位完了只剩个位
	} 
	if(x == 1) c[lenc++] = x;
	// 把加出来的结果，转换为字符串
	for(int i=0;i<lenc;i++){
		c1 = char(c[i]+'0') + c1;
	}
	return c1;
}