#include <stdio.h>
int function(int n){
    int prev = 0;
    int curr = 1;
    int next;
    int count = 2;
    do{
        next = prev+curr;
        prev = curr;
        curr = next;
        count = count + 1;
    }
    while(count <= n);
    return count;
}
int main(void) {
    printf("%d\n",function(1));
    return 0;
}