为啥只对了两个

#include <bits/stdc++.h>
using namespace std;
int sum(int a){
    int s=0;
    while(a!=0){
        s++;
        a/=10;
    }
    return s;
}
int main(){
    long long n,a,b,base=1;
    string s;
    char c;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>s;
        if(isalpha(s[0])){
            c=s[0];
            cin>>a>>b;
            switch(c){
                case 'a':printf("%d+%d=%d\n%d\n",a,b,a+b,sum(a)+sum(b)+sum(a+b)+2);break;
                case 'b':printf("%d-%d=%d\n%d\n",a,b,a-b,sum(a)+sum(b)+sum(a-b)+2);break;
                case 'c':printf("%d*%d=%d\n%d\n",a,b,a*b,sum(a)+sum(b)+sum(a*b)+2);break;
            } 
        } 
        else{
            base=1;
            a=0;
            for(int i=s.size()-1;i>=0;i--){
                a+=(s[i]-'0')*base;
                base*=10;
            }
            cin>>b;
            switch(c){
                case 'a':printf("%d+%d=%d\n%d\n",a,b,a+b,sum(a)+sum(b)+sum(a+b)+2);break;
                case 'b':printf("%d-%d=%d\n%d\n",a,b,a-b,sum(a)+sum(b)+sum(a-b)+2);break;
                case 'c':printf("%d*%d=%d\n%d\n",a,b,a*b,sum(a)+sum(b)+sum(a*b)+2);break;
            } 
        }
    }
    return 0;
}

我下载了测试点发现自己也没有错误啊？