Fibonacci sequence

#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    int i,n=51;
    long int a=0,b=1;
    for(i=0;i<n;){
        cout<<setw(2)<<i++<<" : "<<a<<"\n";
        a=a+b; b=a-b;
    }
    return 0;
}