95分#16 TLE，求助

#include<iostream>
#include<cmath>
#define int long long
using namespace std;
int change(int x,int base)
{
    int tmp = 0;
    int i = 0;
    while(x >= 10)
    {
        tmp += (x % 10) * pow(base,i);
        x /= 10;
        i++;
    }
    if(x < 10)tmp += x * pow(base,i);
    return tmp;
}
int big(int x)
{
    int tmp = 0;
    while(x >= 10)
    {
        tmp = max( tmp , x % 10 );
        x /= 10;
    }
    if(x < 10)tmp = max(tmp , x);
    return tmp;
}
int Base(int x,int y,int res)
{
    int tmp = 0;
    int a,b,c;
    int p;
    p = max(max(big(x),big(y)),big(res));
    for(int i = p+1 ; i <= res+1 ; i++)
    {
        a = change(x,i);
        b = change(y,i);
        c = change(res,i);
        if(a*b==c){tmp = i;break;}
    }
    return tmp;
}
signed main()
{
    int x,y,res;
    cin >> x >> y >> res;
    cout << Base(x,y,res);
    return 0;
}