P1314 求多个分数的和

#include <bits/stdc++.h>
using namespace std;
int gcd(int a,int b) {
    if(b==0){
        return a;
    }else{
        return gcd(b,a%b);
    }
}
int main() {
    string n;
    getline(cin,n);
    string a,x,y;
    int p,q,p1,q1,c;
    while(n.find('+')>=0 && n.find('+')<n.size()){
        c = n.find('+',n.find('+')+1);
        if(c>=0 && c<n.size()){
            a = n.substr(0,c);
            n = n.substr(c);
        }else{
            a = n;
            n = "";
        }
        x = a.substr(0,a.find('+'));
        y = a.substr(a.find('+')+1);
        p = stoi(x.substr(0,x.find('/')));
        p1 = stoi(x.substr(x.find('/')+1));
        q = stoi(y.substr(0,y.find('/')));
        q1 = stoi(y.substr(y.find('/')+1));
        int gcd1 = gcd(max(p1,q1),min(p1,q1));
        int lcm = p1*q1/gcd1;
        p *= lcm/p1;
        q *= lcm/q1;
        p1 = lcm;
        q1 = lcm;
        p += q;
        gcd1 = gcd(max(p,p1),min(p,p1));
        p /= gcd1;
        p1 /= gcd1;
        if(p1!=1){
            n = to_string(p)+"/"+to_string(p1)+n;
        }else{
            n = to_string(p)+n;
        }
    }
    cout<<n;
    return 0;
}