#include using namespace std; //-------------------------------------------- #define FOR(i,a,b) for(int i=(a);i<(b);i++) #define RFOR(i,a,b) for(int i=(b)-1;i>=(a);i--) #define REP(i,n) FOR(i,0,n) #define RREP(i,n) RFOR(i,0,n) #define LL long long #define INF INT_MAX/3 //-------------------------------------------- const double EPS = 1e-14; const double PI = acos(-1.0); //-------------------------------------------- int main(){ int b[10]; REP (i,9) scanf("%d",&b[i]); REP (i,9) { if (i + 1 != b[i]){ printf("%d\n",i + 1); exit(0); } } printf("10\n"); }