"lucky four" question problem

WHY IT IS SHOWING RUN TIME ERROR FOR THIS SIMPLE CODE
#include

using namespace std;

int main()
{
int t,n,temp,i,str[1000];
cin>>t;
for(i=0;i<t;i++)
{ str[i]=0;
cin>>n;
while(n>0)
{
temp=n%10;
if(temp==4)
str[i]=str[i]+1;
n=n/10;
}
}
for(int k=0;k<t;k++)
{
cout<<"\n"<<str[k];
}
return 0;
}

What does this part right after the first for loop mean?

{=""