#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define getrp() ({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define rd_skip() while(*rp++>=48)
#define wt(v) ({ulong _z=v;do*--wp=_z%10+48;while(_z/=10);})
#define wt1(v) ({char wbuf[64],*wp=wbuf+sizeof wbuf;wt(v);write(1,wp,wbuf+sizeof wbuf-wp);})
#define rep3(v,s,e) for(long v=s;v<e;++v)

typedef unsigned long ulong;

ulong a[256];

int main(){
	char*rp=getrp();
	rd_skip();
	for(long c;c=*rp;rp+=2){
		a[c]+=1;
	}
	ulong z=0;
	rep3(i,1,9){
		ulong k=a[i+48];
		rep3(j,1,9){
			k*=i;
			z+=a[j+48]*k;
		}
	}
	wt1(z);
	_exit(0);
}