de ce nu merge main-ul? :@

nu inteleg ce este gresit la programul asta :@ 

#include<iostream>
using namespace std;
int main(){
   int i,a,b;
   cin>>a,b;
   if(a>=b){
      for(i=b;i!=0;i--)
         if(a%i==0&&b%i==0){
            cout<<i;
            break;
         }
   }
   else
      if(a<=b){
         for(i=a;i!=0;i--)
         if(a%i==0&&b%i==0){
            cout<<i;
            break;
         }
      }
}