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

#define rd_init() char*rp=({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);})

typedef unsigned long ulong;

int main(){
	rd_init();
	rd_skip();
	long x;
	long a=0,c=0;
	for(char*p=rp;x=*p++,x!=10;){
		c+=x!='A';
	}
	long u=0,v=0;
	for(char*p=rp;x=*p++,x!=10;){
		if(x=='A'||x!='C'&&a<c){
			u+=1;
		}else{
			v+=u;
		}
		c-=x!='A';
		a+=x!='C';
	}
	wt1(v);
	_exit(0);
}