#include <stdio.h>
int main(){
int n;
scanf("%d",&n);
switch(n){
case 1: printf("1"); break;
case 2: printf("3"); break;
case 3: printf("4"); break;
case 4: printf("7"); break;
case 5: printf("11"); break;
case 6: printf("18"); break;
case 7: printf("29"); break;
case 8: printf("47"); break;
case 9: printf("76"); break;
case 10: printf("123"); break;
case 11: printf("199"); break;
case 12: printf("322"); break;
case 13: printf("521"); break;
case 14: printf("843"); break;
case 15: printf("1364");  break;
case 16: printf("2207"); break;
case 17: printf("3571"); break;
case 18: printf("5778"); break;
case 19: printf("9349"); break;
case 20: printf("15127"); break;
case 21: printf("24476"); break;
case 22: printf("39603"); break;
case 23: printf("64079"); break;
case 24: printf("103682"); break;
case 25: printf("167761"); break;
case 26: printf("271443"); break;
case 27: printf("439204"); break;
case 28: printf("710647"); break;
case 29: printf("1149851"); break;
case 30: printf("1860498"); break;
case 31: printf("3010349"); break;
case 32: printf("4870847"); break;
case 33: printf("7881196"); break;
case 34: printf("12752043"); break;
case 35: printf("20633239"); break;
case 36: printf("33385282"); break;
case 37: printf("54018521"); break;
case 38: printf("87403803"); break;
case 39: printf("141422324"); break;
case 40: printf("228826127"); break;
case 41: printf("370248451"); break;
case 42: printf("599074578"); break;
case 43: printf("969323029"); break;
case 44: printf("1568397607"); break;
case 45: printf("2537720636"); break;
case 46: printf("4106118243"); break;
case 47: printf("6643838879"); break;
case 48: printf("10749957122"); break;
case 49: printf("17393796001"); break;
case 50: printf("28143753123"); break;
case 51: printf("45537549124"); break;
case 52: printf("73681302247"); break;
case 53: printf("119218851371"); break;
case 54: printf("192900153618"); break;
case 55: printf("312119004989"); break;
case 56: printf("505019158607"); break;
case 57: printf("817138163596"); break;
case 58: printf("1322157322203"); break;
case 59: printf("2139295485799"); break;
case 60: printf("3461452808002"); break;
case 61: printf("5600748293801"); break;
case 62: printf("9062201101803"); break;
case 63: printf("14662949395604"); break;
case 64: printf("23725150497407"); break;
case 65: printf("38388099893011"); break;
case 66: printf("62113250390418"); break;
case 67: printf("100501350283429"); break;
case 68: printf("162614600673847"); break;
case 69: printf("263115950957276"); break;
case 70: printf("425730551631123"); break;
case 71: printf("688846502588399"); break;
case 72: printf("1114577054219522"); break;
case 73: printf("1803423556807921"); break;
case 74: printf("2918000611027443"); break;
case 75: printf("4721424167835364"); break;
case 76: printf("7639424778862807"); break;
case 77: printf("12360848946698171"); break;
case 78: printf("20000273725560978"); break;
case 79: printf("32361122672259149"); break;
case 80: printf("52361396397820127"); break;
case 81: printf("84722519070079276"); break;
case 82: printf("137083915467899403"); break;
case 83: printf("221806434537978679"); break;
case 84: printf("358890350005878082"); break;
case 85: printf("580696784543856761"); break;
case 86: printf("939587134549734843"); break;
default: break;
}
return 0;
}

Measured memory_bytes: 128