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

int main(int argc,char*argv[]){
    if(argc<2)
    {
        return 0;
    }
    int n=atoi(argv[1]);
    }
    
    if(n<1 || n>10)
    {
        printf("Invalid input");
        return 0;
    }
    
    if(Argc!=n+1){
    }
    
    long long expected_sum=(long long)n*(n+1)/2;
    long long actual_Sum=0;
    
    for(int i=2;i<argc;i++)
    {
        int current_car_number = atoi(argv[i]);
    }
    
    if(current_car_number<1 || current_car_number>n || argv[i][0] == '-')
    {
        printf("Invalid input\n");
        return 0;
    }
    
    actual_sum+=current_car_number;
    }
    
    int missing_integer=(int)(expected_sum - actual_sum);
    printf("%d\n",missing_integer);
    
return 0;
}