View Code of Problem 23

#include <stdio.h>
int main(){
  int M;
  while(~scanf("%d",&M)){
    int a[1000],i;
    if(M==0) break;
    a[0]=1;
    a[2]=2;
    for(i=2;i<1000;i++)
      a[i]=a[i-1]+a[i-2];
    printf("%d\n",a[M-1]);
  }

}