跳台阶问题

#include <stdio.h>
#include <stdlib.h>

int ttj(int n){
    int n1;
    int n2;
    if(n == 1) return 1;
    if(n == 2) return 2;
    n1 = ttj(n - 1);
    n2 = ttj(n - 2);
    return n2 + n1;
}

main(){
    int num;
    num = ttj(3);
    printf("%d",num);
}