error

#include <stdio.h>

void swap (int *x, int *y);
int Add(int x, int y);

int main(void)
{
    int x1 = 50000;
    int y1 = 100000;
    int z1 = 80000;

    printf("before x1 = %d, y1 = %d\n", x1, y1);

    swap(x1, y1);
    z1 = Add(x1, x2);

    printf("after x1 = %d, y1 = %d\n", x1, y1);

    return 0;
}

void swap(int x, int y)
{
    int temp;

    temp = *x;
    *x = *y;
    *y = temp;
}

void Add(int x, int y)
{
    int z;

    z = x + y;
    return z;
}