#include <unistd.h>
static char inBuf[1 << 10];
static int inLen = 0, inPos = 0;
inline int readChar() {
if (inPos == inLen) {
inLen = read(0, inBuf, sizeof(inBuf));
inPos = 0;
if (inLen <= 0) return -1;
}
return inBuf[inPos++];
}
inline int readInt() {
int c = readChar();
while (c <= ' ') { if (c == -1) return -1; c = readChar(); }
int x = 0;
while (c > ' ') {
x = x * 10 + (c - '0');
c = readChar();
}
return x;
}
int main() {
int a[105];
int n = 0;
int v;
while ((v = readInt()) != -1) {
a[n++] = v;
}
int y = a[--n];
int x = a[--n];
int ans = a[x - 1] + a[y - 1];
}
