求助，我真觉得一点毛病都没有

#include <iostream>
#include<vector>
#include<string>
using namespace std;
int main()
{
    string s;
    int i=0,x;
    char a[3]={0,0,0};
    cin>>s;
    while(i<s.length())
    {
        if(s[i]=='a')
            a[0]=s[i+3];
            if(s[i]=='b')
            a[1]=s[i+3];
            if(s[i]=='c')
            a[2]=s[i+3];
        i++;
    }
    for(int i=0;i<3;i++)
        cout<<a[i]<<" ";
}