Recursive program

[t1mu]

why does this program go so slow?

#include<iostream.h>
int fib(int n){
if(n==1 || n==2) return 1;
return fib(n-1)+fib(n-2);
};

void main(){
for(int i=1; i<70; i++)
cout<<" fib("<<i<<") = "<<fib(i)<<endl;
}