請問為甚麼是CE

我用了debug他說第一行就錯了

想請各位大大幫個忙

include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) {
int a,b,;
while (cin>>a>>b)
{
int c=1
for(int i=2;i<=a;i,=b,i++)
if(a%i==0&&b%i==0)
{
c=i;
}

cout<<i<<endl;

}

return 0;
}

#